<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<link:linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <link:roleRef roleURI="http://www.pentair.com/role/Acquisitions" xlink:href="pnr-20200331.xsd#Acquisitions" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/AcquisitionsAcquisitionsDetails" xlink:href="pnr-20200331.xsd#AcquisitionsAcquisitionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatements" xlink:href="pnr-20200331.xsd#BasisOfPresentationAndResponsibilityForInterimFinancialStatements" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatementsAdoptionOfNewAccountingStandardsDetails" xlink:href="pnr-20200331.xsd#BasisOfPresentationAndResponsibilityForInterimFinancialStatementsAdoptionOfNewAccountingStandardsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatementsTables" xlink:href="pnr-20200331.xsd#BasisOfPresentationAndResponsibilityForInterimFinancialStatementsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BenefitPlans" xlink:href="pnr-20200331.xsd#BenefitPlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BenefitPlansDetail" xlink:href="pnr-20200331.xsd#BenefitPlansDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/BenefitPlansTables" xlink:href="pnr-20200331.xsd#BenefitPlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CommitmentsAndContingencies" xlink:href="pnr-20200331.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CommitmentsAndContingenciesAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#CommitmentsAndContingenciesAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CommitmentsAndContingenciesChangesInCarryingAmountOfServiceAndProductWarrantiesDetail" xlink:href="pnr-20200331.xsd#CommitmentsAndContingenciesChangesInCarryingAmountOfServiceAndProductWarrantiesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CommitmentsAndContingenciesTables" xlink:href="pnr-20200331.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedBalanceSheets" xlink:href="pnr-20200331.xsd#CondensedConsolidatedBalanceSheets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:href="pnr-20200331.xsd#CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:href="pnr-20200331.xsd#CondensedConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedStatementsOfChangesInEquity" xlink:href="pnr-20200331.xsd#CondensedConsolidatedStatementsOfChangesInEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:href="pnr-20200331.xsd#CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/CoverPage" xlink:href="pnr-20200331.xsd#CoverPage" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/Debt" xlink:href="pnr-20200331.xsd#Debt" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DebtAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#DebtAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DebtDebtAndAverageInterestRatesOnDebtOutstandingDetail" xlink:href="pnr-20200331.xsd#DebtDebtAndAverageInterestRatesOnDebtOutstandingDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DebtDebtOutstandingMaturesOnCalendarYearBasisDetail" xlink:href="pnr-20200331.xsd#DebtDebtOutstandingMaturesOnCalendarYearBasisDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DebtTables" xlink:href="pnr-20200331.xsd#DebtTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesAndFinancialInstruments" xlink:href="pnr-20200331.xsd#DerivativesAndFinancialInstruments" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#DerivativesAndFinancialInstrumentsAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueDetail" xlink:href="pnr-20200331.xsd#DerivativesAndFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsRecordedAmountsAndEstimatedFairValuesDetail" xlink:href="pnr-20200331.xsd#DerivativesAndFinancialInstrumentsRecordedAmountsAndEstimatedFairValuesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsTables" xlink:href="pnr-20200331.xsd#DerivativesAndFinancialInstrumentsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/EarningsPerShare" xlink:href="pnr-20200331.xsd#EarningsPerShare" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/EarningsPerShareBasicAndDilutedEarningsPerShareDetail" xlink:href="pnr-20200331.xsd#EarningsPerShareBasicAndDilutedEarningsPerShareDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/EarningsPerShareTables" xlink:href="pnr-20200331.xsd#EarningsPerShareTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssets" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssets" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssetsAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsChangesInCarryingAmountOfGoodwillBySegmentDetail" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssetsChangesInCarryingAmountOfGoodwillBySegmentDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsDetailOfIdentifiableIntangibleAssetsDetail" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssetsDetailOfIdentifiableIntangibleAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsEstimatedFutureAmortizationExpenseForIdentifiableIntangibleAssetsDetail" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssetsEstimatedFutureAmortizationExpenseForIdentifiableIntangibleAssetsDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsTables" xlink:href="pnr-20200331.xsd#GoodwillAndOtherIdentifiableIntangibleAssetsTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/IncomeTaxes" xlink:href="pnr-20200331.xsd#IncomeTaxes" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/IncomeTaxesAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#IncomeTaxesAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/Restructuring" xlink:href="pnr-20200331.xsd#Restructuring" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringAccrualActivityDetail" xlink:href="pnr-20200331.xsd#RestructuringAccrualActivityDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#RestructuringAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringCostsIncludedInSellingGeneralAdministrativeExpensesDetail" xlink:href="pnr-20200331.xsd#RestructuringCostsIncludedInSellingGeneralAdministrativeExpensesDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringTables" xlink:href="pnr-20200331.xsd#RestructuringTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/Revenue" xlink:href="pnr-20200331.xsd#Revenue" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RevenueAdditionalInformationDetails" xlink:href="pnr-20200331.xsd#RevenueAdditionalInformationDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RevenueGeographicNetSalesInformationBySegmentDetails" xlink:href="pnr-20200331.xsd#RevenueGeographicNetSalesInformationBySegmentDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RevenuePerformanceObligationsDetails" xlink:href="pnr-20200331.xsd#RevenuePerformanceObligationsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RevenueScheduleOfContractAssetsAndLiabilitiesDetails" xlink:href="pnr-20200331.xsd#RevenueScheduleOfContractAssetsAndLiabilitiesDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/RevenueTables" xlink:href="pnr-20200331.xsd#RevenueTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformation" xlink:href="pnr-20200331.xsd#SegmentInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformationFinancialInformationByReportableSegmentDetail" xlink:href="pnr-20200331.xsd#SegmentInformationFinancialInformationByReportableSegmentDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformationReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedDetails" xlink:href="pnr-20200331.xsd#SegmentInformationReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformationTables" xlink:href="pnr-20200331.xsd#SegmentInformationTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlans" xlink:href="pnr-20200331.xsd#SharePlans" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#SharePlansAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansScheduleOfShareBasedCompensationExpenseDetails" xlink:href="pnr-20200331.xsd#SharePlansScheduleOfShareBasedCompensationExpenseDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansScheduleOfValuationAssumptionsDetails" xlink:href="pnr-20200331.xsd#SharePlansScheduleOfValuationAssumptionsDetails" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansTables" xlink:href="pnr-20200331.xsd#SharePlansTables" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/ShareholdersEquity" xlink:href="pnr-20200331.xsd#ShareholdersEquity" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/ShareholdersEquityAdditionalInformationDetail" xlink:href="pnr-20200331.xsd#ShareholdersEquityAdditionalInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SupplementalBalanceSheetInformation" xlink:href="pnr-20200331.xsd#SupplementalBalanceSheetInformation" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SupplementalBalanceSheetInformationDetail" xlink:href="pnr-20200331.xsd#SupplementalBalanceSheetInformationDetail" xlink:type="simple" />
  <link:roleRef roleURI="http://www.pentair.com/role/SupplementalBalanceSheetInformationTables" xlink:href="pnr-20200331.xsd#SupplementalBalanceSheetInformationTables" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/Acquisitions" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/AcquisitionsAcquisitionsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionLineItems" xlink:label="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable" xlink:label="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6A3927FFF290CFCB3EEFC6D444451E71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6A3927FFF290CFCB3EEFC6D444451E71" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAxis" xlink:label="loc_us-gaap_BusinessAcquisitionAxis_16E3367C63F3DD6D4D5BC6D444465EF5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfBusinessAcquisitionsByAcquisitionTable_6A3927FFF290CFCB3EEFC6D444451E71" xlink:to="loc_us-gaap_BusinessAcquisitionAxis_16E3367C63F3DD6D4D5BC6D444465EF5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_16E3367C63F3DD6D4D5BC6D444465EF5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionAcquireeDomain" xlink:label="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BusinessAcquisitionAxis_16E3367C63F3DD6D4D5BC6D444465EF5" xlink:to="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_AquionMember" xlink:label="loc_pnr_AquionMember_2744DAEB6F987AD43D43C6D44446279B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873" xlink:to="loc_pnr_AquionMember_2744DAEB6F987AD43D43C6D44446279B" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_PelicanMember" xlink:label="loc_pnr_PelicanMember_F8A2D31EF91CD3C11CEEC6D4444655A1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionAcquireeDomain_2B0326BBFACE85E84C01C6D444462873" xlink:to="loc_pnr_PelicanMember_F8A2D31EF91CD3C11CEEC6D4444655A1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired" xlink:label="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_9DACE6312097EB634689C6D444471975" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_PaymentsToAcquireBusinessesNetOfCashAcquired_9DACE6312097EB634689C6D444471975" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_5E58BEDDA94018C966BAC6D444476AFE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_Goodwill_5E58BEDDA94018C966BAC6D444476AFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount" xlink:label="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_716C183DE52DCD3E081AC6D444475D4A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_BusinessAcquisitionPurchasePriceAllocationGoodwillExpectedTaxDeductibleAmount_716C183DE52DCD3E081AC6D444475D4A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_20DC8E351CB1C64E242EC6D444485B3B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIndefiniteLivedIntangibleAssets_20DC8E351CB1C64E242EC6D444485B3B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles" xlink:label="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_2B75AD012E60FB48D7BCC6D44448449A" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_BusinessCombinationRecognizedIdentifiableAssetsAcquiredAndLiabilitiesAssumedIntangibles_2B75AD012E60FB48D7BCC6D44448449A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetUsefulLife" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_F77A945E555ACE901985C6D444488B74" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BusinessAcquisitionLineItems_79A0F2F7AB00B548870BC6D44447F4B7" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetUsefulLife_F77A945E555ACE901985C6D444488B74" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatements" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatementsAdoptionOfNewAccountingStandardsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/BasisOfPresentationAndResponsibilityForInterimFinancialStatementsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/BenefitPlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/BenefitPlansDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/BenefitPlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CommitmentsAndContingencies" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_7BD7FE6B9C645D61BA60CF1B66D94809" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_2DFBBA6BC3965B7598B2972E8988DF19" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_7BD7FE6B9C645D61BA60CF1B66D94809" xlink:to="loc_us-gaap_StatementTable_2DFBBA6BC3965B7598B2972E8988DF19" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_0E19148542F55965A24B1EF3D497214B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_2DFBBA6BC3965B7598B2972E8988DF19" xlink:to="loc_dei_LegalEntityAxis_0E19148542F55965A24B1EF3D497214B" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_1C4B7BFBA2FAF5D0C58FD7C9A7B22EDA_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_0E19148542F55965A24B1EF3D497214B" xlink:to="loc_dei_EntityDomain_1C4B7BFBA2FAF5D0C58FD7C9A7B22EDA_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_44F3AEA879365E2B9F315672BDCEB7F3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_0E19148542F55965A24B1EF3D497214B" xlink:to="loc_dei_EntityDomain_44F3AEA879365E2B9F315672BDCEB7F3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommitmentsAndContingenciesDisclosureTextBlock" xlink:label="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_5509336E159F5920B599C5838F1B86E5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_7BD7FE6B9C645D61BA60CF1B66D94809" xlink:to="loc_us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_5509336E159F5920B599C5838F1B86E5" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/CommitmentsAndContingenciesAdditionalInformationDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CommitmentsAndContingenciesChangesInCarryingAmountOfServiceAndProductWarrantiesDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedBalanceSheets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedBalanceSheetsParenthetical" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedStatementsOfChangesInEquity" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_9135ED7B670C3C8E91B2C69C8E80D19F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_560271326E0CCCE64337C69C8E7E34E7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_9135ED7B670C3C8E91B2C69C8E80D19F" xlink:to="loc_us-gaap_StatementTable_560271326E0CCCE64337C69C8E7E34E7" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_4CC9EB98933A04F703E1C69C8E7E34DD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_560271326E0CCCE64337C69C8E7E34E7" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_4CC9EB98933A04F703E1C69C8E7E34DD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4CC9EB98933A04F703E1C69C8E7E34DD" xlink:to="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_4CC9EB98933A04F703E1C69C8E7E34DD" xlink:to="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_B1CC676E9C68C3E59699C69C8E7F94AC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:to="loc_us-gaap_CommonStockMember_B1CC676E9C68C3E59699C69C8E7F94AC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_C1EA7CC88BEEBAE43476C69C8E7FCD9E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_C1EA7CC88BEEBAE43476C69C8E7FCD9E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_6C43D166B32E38B9E5F8C69C8E7FFF33" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:to="loc_us-gaap_RetainedEarningsMember_6C43D166B32E38B9E5F8C69C8E7FFF33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1FE0EC733484997F35A1C69C8E80CF5E" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_B3692BBAB56318F285AAC69C8E7E4146" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_1FE0EC733484997F35A1C69C8E80CF5E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_C4E5EC68F77B1A2F0662C69C8E80878C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9135ED7B670C3C8E91B2C69C8E80D19F" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_C4E5EC68F77B1A2F0662C69C8E80878C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_9135ED7B670C3C8E91B2C69C8E80D19F" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_1FFFCBF7E2B57B1FF0D8C69C8E80565A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_SharesOutstanding_1FFFCBF7E2B57B1FF0D8C69C8E80565A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_A4B0768944D2134E664FC69C8E8117B1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_A4B0768944D2134E664FC69C8E8117B1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_B8ED1D23972AB516D5F7C69C8E81000C" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_ProfitLoss_B8ED1D23972AB516D5F7C69C8E81000C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_FA0AA865BB23ABF55D9CC69C8E81AFDD" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_FA0AA865BB23ABF55D9CC69C8E81AFDD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsCommonStock" xlink:label="loc_us-gaap_DividendsCommonStock_8530CAA4DC1651341A01C69C8E814ED9" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_DividendsCommonStock_8530CAA4DC1651341A01C69C8E814ED9" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_E72FDDF09DA014E03C84C69C8E81200F" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_E72FDDF09DA014E03C84C69C8E81200F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_DDCB78339D95E62F092BC69C8E825E6E" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_DDCB78339D95E62F092BC69C8E825E6E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_4D968360655BDEE61FCEC69C8E82C3AE" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_4D968360655BDEE61FCEC69C8E82C3AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_B9662D0F37EEBE576547C69C8E8269F1" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_B9662D0F37EEBE576547C69C8E8269F1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_FA18D0E2EA6C8A222576C69C8E820D21" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_FA18D0E2EA6C8A222576C69C8E820D21" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_52E947A7D67B8871B094C69C8E83B48C" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_52E947A7D67B8871B094C69C8E83B48C" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SharesSurrenderedByEmployeesShares" xlink:label="loc_pnr_SharesSurrenderedByEmployeesShares_3E3D7B9EEC3C20D08962C69C8E83CA52" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_pnr_SharesSurrenderedByEmployeesShares_3E3D7B9EEC3C20D08962C69C8E83CA52" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SharesSurrenderedByEmployees" xlink:label="loc_pnr_SharesSurrenderedByEmployees_98D9D87ED98359790A2CC69C8E830C1C" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_pnr_SharesSurrenderedByEmployees_98D9D87ED98359790A2CC69C8E830C1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_51ED0405FF84946A6E61C69C8E836E9A" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4B6F0A1C99348F8C22AEC69C8E80F6D5" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_51ED0405FF84946A6E61C69C8E836E9A" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/CoverPage" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/Debt" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityAxis" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_C1CFAE07E6ACFC13058EC69C8CCB4FAF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_C1CFAE07E6ACFC13058EC69C8CCB4FAF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_64D09F5DC6ADA52DA589C69C8CCC70BC_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_C1CFAE07E6ACFC13058EC69C8CCB4FAF" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_64D09F5DC6ADA52DA589C69C8CCC70BC_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityLenderDomain" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_64D09F5DC6ADA52DA589C69C8CCC70BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_C1CFAE07E6ACFC13058EC69C8CCB4FAF" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_64D09F5DC6ADA52DA589C69C8CCC70BC" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_OtherCreditFacilitiesMember" xlink:label="loc_pnr_OtherCreditFacilitiesMember_8F1D9C4908A0FC10FC9BC69C8CCC649D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_64D09F5DC6ADA52DA589C69C8CCC70BC" xlink:to="loc_pnr_OtherCreditFacilitiesMember_8F1D9C4908A0FC10FC9BC69C8CCC649D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_FC3AB8A4F2935166A706C69C8CD1ECBB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_FC3AB8A4F2935166A706C69C8CD1ECBB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_FC3AB8A4F2935166A706C69C8CD1ECBB" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_FC3AB8A4F2935166A706C69C8CD1ECBB" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_C833940D76551891818DC69C8CD22B9A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:to="loc_us-gaap_LineOfCreditMember_C833940D76551891818DC69C8CD22B9A" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_TermLoansMember" xlink:label="loc_pnr_TermLoansMember_B121F4CF587A5466946EC69C8CD2F6CE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:to="loc_pnr_TermLoansMember_B121F4CF587A5466946EC69C8CD2F6CE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_A3A4E05D4F5CDA19548AC69C8CD2879D" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:to="loc_us-gaap_CommercialPaperMember_A3A4E05D4F5CDA19548AC69C8CD2879D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_26B7E0F782A3C113DDA2C69C8CD36440" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_C369AB53B1D2133B2FDEC69C8CD10B9F" xlink:to="loc_us-gaap_SeniorNotesMember_26B7E0F782A3C113DDA2C69C8CD36440" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_583EB34D625A7C60BC2BC69C8CD3A6CA" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:to="loc_us-gaap_CreditFacilityAxis_583EB34D625A7C60BC2BC69C8CD3A6CA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5D0C0247F32E1651BDE6C69C8CD3CE89_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_583EB34D625A7C60BC2BC69C8CD3A6CA" xlink:to="loc_us-gaap_CreditFacilityDomain_5D0C0247F32E1651BDE6C69C8CD3CE89_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5D0C0247F32E1651BDE6C69C8CD3CE89" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_583EB34D625A7C60BC2BC69C8CD3A6CA" xlink:to="loc_us-gaap_CreditFacilityDomain_5D0C0247F32E1651BDE6C69C8CD3CE89" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_037A0FC7F003BD34940EC69C8CD34F13" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_5D0C0247F32E1651BDE6C69C8CD3CE89" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_037A0FC7F003BD34940EC69C8CD34F13" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_62999DFD523AD9444C94C69C8CD3B1AE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:to="loc_srt_RangeAxis_62999DFD523AD9444C94C69C8CD3B1AE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_62999DFD523AD9444C94C69C8CD3B1AE" xlink:to="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_62999DFD523AD9444C94C69C8CD3B1AE" xlink:to="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_78D99945E2EF3A8C2626C69C8CD48D3F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C" xlink:to="loc_srt_MaximumMember_78D99945E2EF3A8C2626C69C8CD48D3F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_F9FA736063560018D472C69C8CD4FE62" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_6AF2CAFC00FC8C12B98EC69C8CD42C0C" xlink:to="loc_srt_MinimumMember_F9FA736063560018D472C69C8CD4FE62" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_259764FF0556C5F9564BC69C8CD57640" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_88C75D2CEE6C18E65EEDC69C8CCBF27C" xlink:to="loc_us-gaap_DebtInstrumentAxis_259764FF0556C5F9564BC69C8CD57640" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_259764FF0556C5F9564BC69C8CD57640" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_259764FF0556C5F9564BC69C8CD57640" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_TermLoans2.914duein2023Member" xlink:label="loc_pnr_TermLoans2.914duein2023Member_E13BBEC3AD6632615A19C69C8CD546D9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF" xlink:to="loc_pnr_TermLoans2.914duein2023Member_E13BBEC3AD6632615A19C69C8CD546D9" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember" xlink:label="loc_pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember_AC2BAA84304A506235C4C69C8CD5B276" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ED7844314E6889180F29C69C8CD534BF" xlink:to="loc_pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember_AC2BAA84304A506235C4C69C8CD5B276" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_B44E5D969439F02B2168C69C8CD668BC" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_B44E5D969439F02B2168C69C8CD668BC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTerm" xlink:label="loc_us-gaap_DebtInstrumentTerm_F4BC4E48DB1D8A397A08C69C8CD60E3C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_DebtInstrumentTerm_F4BC4E48DB1D8A397A08C69C8CD60E3C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_9705E6AE9E3DD7B88469C69C8CD6F660" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_9705E6AE9E3DD7B88469C69C8CD6F660" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet" xlink:label="loc_us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet_5D0E22B5E4BE0B7A1E71C69C8CD7854C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_LineOfCreditFacilityIncreaseDecreaseForPeriodNet_5D0E22B5E4BE0B7A1E71C69C8CD7854C" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit" xlink:label="loc_pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit_EFC97D6A236121FC94D8C69C8CD72326" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit_EFC97D6A236121FC94D8C69C8CD72326" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_812C7E88911FFA309266C69C8CD69B29" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_812C7E88911FFA309266C69C8CD69B29" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPaper" xlink:label="loc_us-gaap_CommercialPaper_F02B5C5FE35BA65A3DBAC69C8CD73D34" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_CommercialPaper_F02B5C5FE35BA65A3DBAC69C8CD73D34" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DebtInstrumentCovenantUnrestrictedCash" xlink:label="loc_pnr_DebtInstrumentCovenantUnrestrictedCash_6AAF2B6132C44830F950C69C8CD7DD4E" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_pnr_DebtInstrumentCovenantUnrestrictedCash_6AAF2B6132C44830F950C69C8CD7DD4E" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DebtInstrumentLeverageRatioCovenant" xlink:label="loc_pnr_DebtInstrumentLeverageRatioCovenant_F3468E0A52E1AF03F92FC69C8CD7435B" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_pnr_DebtInstrumentLeverageRatioCovenant_F3468E0A52E1AF03F92FC69C8CD7435B" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DebtInstrumentLeverageRatioCovenantPeriod" xlink:label="loc_pnr_DebtInstrumentLeverageRatioCovenantPeriod_78407C608616CA5D2FCBC69C8CD73382" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_pnr_DebtInstrumentLeverageRatioCovenantPeriod_78407C608616CA5D2FCBC69C8CD73382" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DebtInstrumentEBITDARatioCovenant" xlink:label="loc_pnr_DebtInstrumentEBITDARatioCovenant_22D0E3FF54A45FB855DFC69C8CD8110F" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_pnr_DebtInstrumentEBITDARatioCovenant_22D0E3FF54A45FB855DFC69C8CD8110F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCredit" xlink:label="loc_us-gaap_LineOfCredit_5AAA85F33DE1AD2D4818C69C8CD800A6" xlink:type="locator" />
    <link:definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_LineOfCredit_5AAA85F33DE1AD2D4818C69C8CD800A6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_0E1FB2846B888B32E0DFC69C8CD87767" xlink:type="locator" />
    <link:definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_0E1FB2846B888B32E0DFC69C8CD87767" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtWeightedAverageInterestRate" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_E8CC0EB42D28CABAE275C69C8CD8DB08" xlink:type="locator" />
    <link:definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_E8CC0EB42D28CABAE275C69C8CD8DB08" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_F8986F5E147DC2790CECC69C8CDE2588" xlink:type="locator" />
    <link:definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB0C3A79AA5402ACE08BC69C8CD6A5C4" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_F8986F5E147DC2790CECC69C8CDE2588" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtDebtAndAverageInterestRatesOnDebtOutstandingDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentLineItems" xlink:label="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentTable" xlink:label="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:to="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeAxis" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_391C0B55F6D293FCDFA9C69C8CF780AA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_391C0B55F6D293FCDFA9C69C8CF780AA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_391C0B55F6D293FCDFA9C69C8CF780AA" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtTypeDomain" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_391C0B55F6D293FCDFA9C69C8CF780AA" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPaperMember" xlink:label="loc_us-gaap_CommercialPaperMember_5B2401DC1866F467BF0DC69C8CF8FFA3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:to="loc_us-gaap_CommercialPaperMember_5B2401DC1866F467BF0DC69C8CF8FFA3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LineOfCreditMember" xlink:label="loc_us-gaap_LineOfCreditMember_F2101BE19743BD33C85EC69C8CF8E979" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:to="loc_us-gaap_LineOfCreditMember_F2101BE19743BD33C85EC69C8CF8E979" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_TermLoansMember" xlink:label="loc_pnr_TermLoansMember_A30508C8874A717962C8C69C8CF87B42" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:to="loc_pnr_TermLoansMember_A30508C8874A717962C8C69C8CF87B42" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SeniorNotesMember" xlink:label="loc_us-gaap_SeniorNotesMember_CFEBB0C9578438284326C69C8CF8116D" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_6F858F879B9E56EA4C07C69C8CF78B1B" xlink:to="loc_us-gaap_SeniorNotesMember_CFEBB0C9578438284326C69C8CF8116D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_9597D97571CB433F92BDC69C8CF88D7E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:to="loc_us-gaap_CreditFacilityAxis_9597D97571CB433F92BDC69C8CF88D7E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_50FB5C4E53A23F9AE3FDC69C8CF9492E_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_9597D97571CB433F92BDC69C8CF88D7E" xlink:to="loc_us-gaap_CreditFacilityDomain_50FB5C4E53A23F9AE3FDC69C8CF9492E_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_50FB5C4E53A23F9AE3FDC69C8CF9492E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_9597D97571CB433F92BDC69C8CF88D7E" xlink:to="loc_us-gaap_CreditFacilityDomain_50FB5C4E53A23F9AE3FDC69C8CF9492E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_5FF128FF08A82B95D307C69C8CF94DAD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_50FB5C4E53A23F9AE3FDC69C8CF9492E" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_5FF128FF08A82B95D307C69C8CF94DAD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="loc_us-gaap_DebtInstrumentAxis_6DB221F0905AD57B4A56C69C8CF90838" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:to="loc_us-gaap_DebtInstrumentAxis_6DB221F0905AD57B4A56C69C8CF90838" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_6DB221F0905AD57B4A56C69C8CF90838" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_6DB221F0905AD57B4A56C69C8CF90838" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_TermLoansdue2023Member" xlink:label="loc_pnr_TermLoansdue2023Member_F2E8D27DEBB031FAB3ADC69C8CFAE80A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_TermLoansdue2023Member_F2E8D27DEBB031FAB3ADC69C8CFAE80A" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesThreePointSixTwoFivePercentDueTwentyTwentyMember" xlink:label="loc_pnr_SeniorNotesThreePointSixTwoFivePercentDueTwentyTwentyMember_B7261087AE7C6728A6E5C69C8D00665E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_SeniorNotesThreePointSixTwoFivePercentDueTwentyTwentyMember_B7261087AE7C6728A6E5C69C8D00665E" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesFivePointZeroZeroZeroPercentDueTwentyTwentyOneMember" xlink:label="loc_pnr_SeniorNotesFivePointZeroZeroZeroPercentDueTwentyTwentyOneMember_46D134A7435656CF0EEDC69C8D0092CD" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_SeniorNotesFivePointZeroZeroZeroPercentDueTwentyTwentyOneMember_46D134A7435656CF0EEDC69C8D0092CD" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesThreePointOneFiveZeroPercentDueTwentyTwentyTwoMember" xlink:label="loc_pnr_SeniorNotesThreePointOneFiveZeroPercentDueTwentyTwentyTwoMember_02F7DF99290B8963AE0EC69C8D00BF42" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_SeniorNotesThreePointOneFiveZeroPercentDueTwentyTwentyTwoMember_02F7DF99290B8963AE0EC69C8D00BF42" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember" xlink:label="loc_pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember_8A301A4E48F181FBAA25C69C8D00DB88" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember_8A301A4E48F181FBAA25C69C8D00DB88" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember" xlink:label="loc_pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember_7B442674A75B3AE47B61C69C8D004216" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_C6BB7368674A69DF24A6C69C8CF988E9" xlink:to="loc_pnr_SeniorNotesFourPointFivePercentDueTwentyTwentyNineMember_7B442674A75B3AE47B61C69C8D004216" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_8F0ABAF799B5585B336AC69C8D01A6B2" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_F63153C54EF81874842FC69C8CF7036B" xlink:to="loc_srt_RangeAxis_8F0ABAF799B5585B336AC69C8D01A6B2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_8F0ABAF799B5585B336AC69C8D01A6B2" xlink:to="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_8F0ABAF799B5585B336AC69C8D01A6B2" xlink:to="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_9514BE14490AA83AED45C69C8D01FC5C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C" xlink:to="loc_srt_MinimumMember_9514BE14490AA83AED45C69C8D01FC5C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_6D3BA684195C62355E61C69C8D02AEF7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_5E86B00478845642C7BEC69C8D019F9C" xlink:to="loc_srt_MaximumMember_6D3BA684195C62355E61C69C8D02AEF7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtWeightedAverageInterestRate" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_C355EA0EF8A6F9C09AD9C69C8D02C136" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_C355EA0EF8A6F9C09AD9C69C8D02C136" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommercialPaper" xlink:label="loc_us-gaap_CommercialPaper_E59503EB7F63849E2B2FC69C8D02D286" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:to="loc_us-gaap_CommercialPaper_E59503EB7F63849E2B2FC69C8D02D286" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnamortizedDebtIssuanceExpense" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_CFBB105EBF2C7FE1E26FC69C8D02819B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_CFBB105EBF2C7FE1E26FC69C8D02819B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_62CA0EBF73D89A3380E4C69C8D038E20" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_CB4D923765F6CB6E30BEC69C8D02697E" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_62CA0EBF73D89A3380E4C69C8D038E20" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtDebtOutstandingMaturesOnCalendarYearBasisDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesAndFinancialInstruments" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLineItems" xlink:label="loc_us-gaap_DerivativeLineItems_7759176E4A65542F943BFD0A2383B1A2" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeTable" xlink:label="loc_us-gaap_DerivativeTable_D2782C8062845E34AF8BE89B38D177F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_7759176E4A65542F943BFD0A2383B1A2" xlink:to="loc_us-gaap_DerivativeTable_D2782C8062845E34AF8BE89B38D177F8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeInstrumentRiskAxis" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_929D33B3CE3F5FFD90297F397B3308C3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_D2782C8062845E34AF8BE89B38D177F8" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_929D33B3CE3F5FFD90297F397B3308C3" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5400BA29EA242760A162D1109AD8D78D_E597B6B0CE4B52839B35F2306F460F74" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_929D33B3CE3F5FFD90297F397B3308C3" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5400BA29EA242760A162D1109AD8D78D_E597B6B0CE4B52839B35F2306F460F74" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeContractTypeDomain" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_474BA03673B15FA8A46013D3907CC15C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_929D33B3CE3F5FFD90297F397B3308C3" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_474BA03673B15FA8A46013D3907CC15C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignExchangeContractMember" xlink:label="loc_us-gaap_ForeignExchangeContractMember_6606492C4CE05D849D7C4B930FD30C23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_474BA03673B15FA8A46013D3907CC15C" xlink:to="loc_us-gaap_ForeignExchangeContractMember_6606492C4CE05D849D7C4B930FD30C23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CurrencySwapMember" xlink:label="loc_us-gaap_CurrencySwapMember_C27CA3D3EED35CEEA30ADAA404C68A97" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_474BA03673B15FA8A46013D3907CC15C" xlink:to="loc_us-gaap_CurrencySwapMember_C27CA3D3EED35CEEA30ADAA404C68A97" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeNotionalAmount" xlink:label="loc_us-gaap_DerivativeNotionalAmount_7F81A7A84E22582DAF8283240EBEEF6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_7759176E4A65542F943BFD0A2383B1A2" xlink:to="loc_us-gaap_DerivativeNotionalAmount_7F81A7A84E22582DAF8283240EBEEF6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax" xlink:label="loc_us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax_63B51A28FD98562E92C1458448465024" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_7759176E4A65542F943BFD0A2383B1A2" xlink:to="loc_us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax_63B51A28FD98562E92C1458448465024" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsAssetsAndLiabilitiesMeasuredAtFairValueDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_15AC0FD762C921227A42C1A348C47D0B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_15AC0FD762C921227A42C1A348C47D0B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_74A23DD6E1CD2F4F4DB5C1A348C58EFB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_15AC0FD762C921227A42C1A348C47D0B" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_74A23DD6E1CD2F4F4DB5C1A348C58EFB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_74A23DD6E1CD2F4F4DB5C1A348C58EFB" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_74A23DD6E1CD2F4F4DB5C1A348C58EFB" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_0F750912E7E98C2AF4C6C1A348C5D545" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_0F750912E7E98C2AF4C6C1A348C5D545" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_7A5736D1F86A7CCBEFB0C1A348C6C90D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_7A5736D1F86A7CCBEFB0C1A348C6C90D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_8453BC0787CE23825B07C1A348C62F52" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_8453BC0787CE23825B07C1A348C62F52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember" xlink:label="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_08958B97D61CFCE591DFC1A348C69C50" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_62867411694C90C18BC4C1A348C55508" xlink:to="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_08958B97D61CFCE591DFC1A348C69C50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementFrequencyAxis" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E2032868C4C0D3820D43C1A348C61D4E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_15AC0FD762C921227A42C1A348C47D0B" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E2032868C4C0D3820D43C1A348C61D4E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6A91EF05CC2E70A6ED63C1A348C6084A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E2032868C4C0D3820D43C1A348C61D4E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6A91EF05CC2E70A6ED63C1A348C6084A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementFrequencyDomain" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_6A91EF05CC2E70A6ED63C1A348C6084A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_E2032868C4C0D3820D43C1A348C61D4E" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_6A91EF05CC2E70A6ED63C1A348C6084A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueMeasurementsRecurringMember" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_95372E21193AB3359A2AC1A348C77CE7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_6A91EF05CC2E70A6ED63C1A348C6084A" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_95372E21193AB3359A2AC1A348C77CE7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CostMethodInvestmentsRealizedLosses" xlink:label="loc_us-gaap_CostMethodInvestmentsRealizedLosses_1AAA1B021270348CCB2AC1A348C7015C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_CostMethodInvestmentsRealizedLosses_1AAA1B021270348CCB2AC1A348C7015C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_0C26E83C9C93CFC7F823C1A348C8CD2D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_0C26E83C9C93CFC7F823C1A348C8CD2D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_8153165A0889A012CF9AC1A348C81DF3" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_8153165A0889A012CF9AC1A348C81DF3" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DeferredCompensationPlanAssetsFairValueDisclosure" xlink:label="loc_pnr_DeferredCompensationPlanAssetsFairValueDisclosure_8105F9C92F8BD28AC399C1A348C85C2C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_pnr_DeferredCompensationPlanAssetsFairValueDisclosure_8105F9C92F8BD28AC399C1A348C85C2C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_70D2A9130AD2C524A8DEC1A348C89DCB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_70D2A9130AD2C524A8DEC1A348C89DCB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetImpairmentCharges" xlink:label="loc_us-gaap_AssetImpairmentCharges_269AE781EE0315CC06D8C1DC5B99B247" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_8BBC20E77173EE676A3CC1A348C790BE" xlink:to="loc_us-gaap_AssetImpairmentCharges_269AE781EE0315CC06D8C1DC5B99B247" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsRecordedAmountsAndEstimatedFairValuesDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeLineItems" xlink:label="loc_us-gaap_DerivativeLineItems_0A8DAB31365C5674A2C5535C0E105F1E" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DerivativeTable" xlink:label="loc_us-gaap_DerivativeTable_5D61A4C10C7B5F70A91FD73283C03A55" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_0A8DAB31365C5674A2C5535C0E105F1E" xlink:to="loc_us-gaap_DerivativeTable_5D61A4C10C7B5F70A91FD73283C03A55" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueByMeasurementBasisAxis" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_BED64BAB87245827A7B8C0519E2223BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_5D61A4C10C7B5F70A91FD73283C03A55" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_BED64BAB87245827A7B8C0519E2223BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3471E4387DE769A29827D7C9A82E779E_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_BED64BAB87245827A7B8C0519E2223BB" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_3471E4387DE769A29827D7C9A82E779E_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FairValueDisclosureItemAmountsDomain" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_B1F18D415DF95FE1A603D91C2AC9B738" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_BED64BAB87245827A7B8C0519E2223BB" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_B1F18D415DF95FE1A603D91C2AC9B738" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_98F959A6B9725AFF8FEA4545A26469E2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_B1F18D415DF95FE1A603D91C2AC9B738" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_98F959A6B9725AFF8FEA4545A26469E2" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_A2277056B0555BA1A5B1D0B3C5D2FC23" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_B1F18D415DF95FE1A603D91C2AC9B738" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_A2277056B0555BA1A5B1D0B3C5D2FC23" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_567D117D9C2554FFB6C4C9751BF21431" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_B1F18D415DF95FE1A603D91C2AC9B738" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_567D117D9C2554FFB6C4C9751BF21431" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtPercentageBearingVariableInterestAmount" xlink:label="loc_us-gaap_LongtermDebtPercentageBearingVariableInterestAmount_E09734005D265447A3F024406B8CAC8B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0A8DAB31365C5674A2C5535C0E105F1E" xlink:to="loc_us-gaap_LongtermDebtPercentageBearingVariableInterestAmount_E09734005D265447A3F024406B8CAC8B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongtermDebtPercentageBearingFixedInterestAmount" xlink:label="loc_us-gaap_LongtermDebtPercentageBearingFixedInterestAmount_26A4C846CF365953B4776403017F19CB" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0A8DAB31365C5674A2C5535C0E105F1E" xlink:to="loc_us-gaap_LongtermDebtPercentageBearingFixedInterestAmount_26A4C846CF365953B4776403017F19CB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_E985B5BD4481529883EE4B0FE2CD1625" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_0A8DAB31365C5674A2C5535C0E105F1E" xlink:to="loc_us-gaap_LongTermDebt_E985B5BD4481529883EE4B0FE2CD1625" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesAndFinancialInstrumentsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/EarningsPerShare" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/EarningsPerShareBasicAndDilutedEarningsPerShareDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/EarningsPerShareTables" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_B91767B2AB0B53B1BB783FC433D64543" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_E8802BC3CFB4514BA80239D99189C3DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_B91767B2AB0B53B1BB783FC433D64543" xlink:to="loc_us-gaap_StatementTable_E8802BC3CFB4514BA80239D99189C3DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_D6B938E31FC356E8AD14B7E10696490B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_E8802BC3CFB4514BA80239D99189C3DA" xlink:to="loc_dei_LegalEntityAxis_D6B938E31FC356E8AD14B7E10696490B" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_820EBF5F5EE17113DA5BD7C9A8622B53_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_D6B938E31FC356E8AD14B7E10696490B" xlink:to="loc_dei_EntityDomain_820EBF5F5EE17113DA5BD7C9A8622B53_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/dei/2019/dei-2019-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_490F67BE9FDC55E38950A5E5F132975A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_D6B938E31FC356E8AD14B7E10696490B" xlink:to="loc_dei_EntityDomain_490F67BE9FDC55E38950A5E5F132975A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock" xlink:label="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_7CED2B1139B85C7DAD04378C3ABB14E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_B91767B2AB0B53B1BB783FC433D64543" xlink:to="loc_us-gaap_ScheduleOfEarningsPerShareBasicAndDilutedTableTextBlock_7CED2B1139B85C7DAD04378C3ABB14E1" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssets" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsAdditionalInformationDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsChangesInCarryingAmountOfGoodwillBySegmentDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillLineItems" xlink:label="loc_us-gaap_GoodwillLineItems_C2F020E67333B9D764FEC69C8D5D848F" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfGoodwillTable" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_AFC55CA7F6C73547C8C1C69C8D5B411D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_C2F020E67333B9D764FEC69C8D5D848F" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_AFC55CA7F6C73547C8C1C69C8D5B411D" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_0C119ECAA83196715443C69C8D5CF78B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_AFC55CA7F6C73547C8C1C69C8D5B411D" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_0C119ECAA83196715443C69C8D5CF78B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0C119ECAA83196715443C69C8D5CF78B" xlink:to="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_0C119ECAA83196715443C69C8D5CF78B" xlink:to="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_ConsumerSolutionsMember" xlink:label="loc_pnr_ConsumerSolutionsMember_7D267202368D74EBB2A9C69C8D5CDCF2" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD" xlink:to="loc_pnr_ConsumerSolutionsMember_7D267202368D74EBB2A9C69C8D5CDCF2" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_IndustrialFlowTechnologiesMember" xlink:label="loc_pnr_IndustrialFlowTechnologiesMember_0C1E07511EF5AB9B52FDC69C8D5D0C53" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_ACFC0F4FB3C45B44D2BBC69C8D5CA4AD" xlink:to="loc_pnr_IndustrialFlowTechnologiesMember_0C1E07511EF5AB9B52FDC69C8D5D0C53" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillRollForward" xlink:label="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_C2F020E67333B9D764FEC69C8D5D848F" xlink:to="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Goodwill" xlink:label="loc_us-gaap_Goodwill_7E9E1F8612E0D1750785C69C8D5E696B" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:to="loc_us-gaap_Goodwill_7E9E1F8612E0D1750785C69C8D5E696B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillPurchaseAccountingAdjustments" xlink:label="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_85E0F222AAECB481E6AEC69C8D5E69FD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:to="loc_us-gaap_GoodwillPurchaseAccountingAdjustments_85E0F222AAECB481E6AEC69C8D5E69FD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillAcquiredDuringPeriod" xlink:label="loc_us-gaap_GoodwillAcquiredDuringPeriod_F83A4672DF0ACB77F7CAC69C8D6329CC" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:to="loc_us-gaap_GoodwillAcquiredDuringPeriod_F83A4672DF0ACB77F7CAC69C8D6329CC" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GoodwillOtherIncreaseDecrease" xlink:label="loc_us-gaap_GoodwillOtherIncreaseDecrease_5C489F2B5DD6778D78D1C69C8D6492EA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_A5293168896DB840E948C69C8D5DF674" xlink:to="loc_us-gaap_GoodwillOtherIncreaseDecrease_5C489F2B5DD6778D78D1C69C8D6492EA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsDetailOfIdentifiableIntangibleAssetsDetail" xlink:type="extended">
    <link:loc xlink:href="pnr-20200331.xsd#pnr_AcquiredIntangibleAssetsByMajorClassLineItems" xlink:label="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:type="locator" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable" xlink:label="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_465E67BFF0A7E49B0D6BC69C8D42089F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_465E67BFF0A7E49B0D6BC69C8D42089F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_A033EF0BFA86CFA74E62C69C8D43ED9F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_465E67BFF0A7E49B0D6BC69C8D42089F" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_A033EF0BFA86CFA74E62C69C8D43ED9F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_A033EF0BFA86CFA74E62C69C8D43ED9F" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_A033EF0BFA86CFA74E62C69C8D43ED9F" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CustomerRelationshipsMember" xlink:label="loc_us-gaap_CustomerRelationshipsMember_F73455E1ADC50FF4DC25C69C8D43A37A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7" xlink:to="loc_us-gaap_CustomerRelationshipsMember_F73455E1ADC50FF4DC25C69C8D43A37A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PatentedTechnologyMember" xlink:label="loc_us-gaap_PatentedTechnologyMember_287F2BB5AABDA4548128C69C8D4493AD" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_0CD2EF5C680EC0C5C6DDC69C8D43A3D7" xlink:to="loc_us-gaap_PatentedTechnologyMember_287F2BB5AABDA4548128C69C8D4493AD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsGross" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_53D606FBA5D049DAED78C69C8D4486BF" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_53D606FBA5D049DAED78C69C8D4486BF" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_DABDEAF0F9FB629F2260C69C8D44BA1F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_DABDEAF0F9FB629F2260C69C8D44BA1F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_FiniteLivedIntangibleAssetsNet" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7CCE87859FFA1ED69944C69C8D458C90" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_7CCE87859FFA1ED69944C69C8D458C90" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_8AE0FC02A4B27586AB8AC69C8D45B711" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_8AE0FC02A4B27586AB8AC69C8D45B711" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_9304F222E90C5017BE42C69C8D4562CD" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_9304F222E90C5017BE42C69C8D4562CD" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_57D4B1D76F045AD87C17C69C8D45B2F0" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_A915ACD5EE805AD0A3E7C69C8D444F4A" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_57D4B1D76F045AD87C17C69C8D45B2F0" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsEstimatedFutureAmortizationExpenseForIdentifiableIntangibleAssetsDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillAndOtherIdentifiableIntangibleAssetsTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/IncomeTaxes" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/IncomeTaxesAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_76AF610CAAA1CB1B02C7C1A348B9B7F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_SubsequentEventTable_76AF610CAAA1CB1B02C7C1A348B9B7F8" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_70F2C9870D40B2C282EAC1A348B912BA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_76AF610CAAA1CB1B02C7C1A348B9B7F8" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_70F2C9870D40B2C282EAC1A348B912BA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3B69D23883DEDD34DDA3C1A348B986ED_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_70F2C9870D40B2C282EAC1A348B912BA" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3B69D23883DEDD34DDA3C1A348B986ED_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_3B69D23883DEDD34DDA3C1A348B986ED" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_70F2C9870D40B2C282EAC1A348B912BA" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_3B69D23883DEDD34DDA3C1A348B986ED" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_A2D7A876278F8A9E974EC1A348B9F715" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_3B69D23883DEDD34DDA3C1A348B986ED" xlink:to="loc_us-gaap_SubsequentEventMember_A2D7A876278F8A9E974EC1A348B9F715" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EffectiveIncomeTaxRateContinuingOperations" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_263C0EB48A4C1531144EC1A348BA2740" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateContinuingOperations_263C0EB48A4C1531144EC1A348BA2740" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_CoronavirusAidReliefandEconomicSecurityActIncomeTaxExpenseBenefit" xlink:label="loc_pnr_CoronavirusAidReliefandEconomicSecurityActIncomeTaxExpenseBenefit_130E87BF6B1346A9091DC1F0FDD2CCE1" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_pnr_CoronavirusAidReliefandEconomicSecurityActIncomeTaxExpenseBenefit_130E87BF6B1346A9091DC1F0FDD2CCE1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense" xlink:label="loc_us-gaap_TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense_41FA4A2A3752E79FAAB7C1F93A4D6CC8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_TaxCutsAndJobsActOf2017TransitionTaxForAccumulatedForeignEarningsIncomeTaxExpense_41FA4A2A3752E79FAAB7C1F93A4D6CC8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_UnrecognizedTaxBenefits" xlink:label="loc_us-gaap_UnrecognizedTaxBenefits_2C7E580204E40B222A9EC1A348BB537C" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_UnrecognizedTaxBenefits_2C7E580204E40B222A9EC1A348BB537C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit" xlink:label="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_52051F42DE0547D10808C1A348BBC3DB" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_TaxCutsAndJobsActOf2017IncomeTaxExpenseBenefit_52051F42DE0547D10808C1A348BBC3DB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent" xlink:label="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent_C89B39D3DCC35FC43FCCC1A348BAC00B" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_46B119ACDCCCF3DD8CEFC1A348BAACD0" xlink:to="loc_us-gaap_EffectiveIncomeTaxRateReconciliationTaxCutsAndJobsActOf2017Percent_C89B39D3DCC35FC43FCCC1A348BAC00B" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/Restructuring" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringAccrualActivityDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_8905236BD2E952E1F3BABD12985316A4" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6289917CB3347DB88CD8BD129852E9DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8905236BD2E952E1F3BABD12985316A4" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6289917CB3347DB88CD8BD129852E9DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_02B8934C671AA3222B03BD129852B597" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_6289917CB3347DB88CD8BD129852E9DA" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_02B8934C671AA3222B03BD129852B597" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_02B8934C671AA3222B03BD129852B597" xlink:to="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_02B8934C671AA3222B03BD129852B597" xlink:to="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_ConsumerSolutionsMember" xlink:label="loc_pnr_ConsumerSolutionsMember_799EDE0BEED8D33FEA07BD14715F0A90" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5" xlink:to="loc_pnr_ConsumerSolutionsMember_799EDE0BEED8D33FEA07BD14715F0A90" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_IndustrialFlowTechnologiesMember" xlink:label="loc_pnr_IndustrialFlowTechnologiesMember_3EE6DCF0F982CCC59543BD14F51ED371" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5" xlink:to="loc_pnr_IndustrialFlowTechnologiesMember_3EE6DCF0F982CCC59543BD14F51ED371" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CorporateAndOtherMember" xlink:label="loc_us-gaap_CorporateAndOtherMember_D7D865EF9125B50B5890BD1298535B72" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_29A58C3E6D8B08F458DABD12985259A5" xlink:to="loc_us-gaap_CorporateAndOtherMember_D7D865EF9125B50B5890BD1298535B72" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated" xlink:label="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated_FB710A6DAB4EC774256CBD1298542BB6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8905236BD2E952E1F3BABD12985316A4" xlink:to="loc_us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminated_FB710A6DAB4EC774256CBD1298542BB6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_B79CA808F111E1F8F4D7BD1298547393" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_8905236BD2E952E1F3BABD12985316A4" xlink:to="loc_us-gaap_RestructuringCharges_B79CA808F111E1F8F4D7BD1298547393" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringCostsIncludedInSellingGeneralAdministrativeExpensesDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveLineItems" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_A400F5E11BC54C39B893C69C8DB42EB0" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_7C0FEE3C38E4AB8BC6CBC69C8DB39F23" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_A400F5E11BC54C39B893C69C8DB42EB0" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_7C0FEE3C38E4AB8BC6CBC69C8DB39F23" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCostAndReserveAxis" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_13D466AD80D8C83342C9C69C8DB3468D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_7C0FEE3C38E4AB8BC6CBC69C8DB39F23" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_13D466AD80D8C83342C9C69C8DB3468D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_AFFF19999FCEEE1B58EAC69C8DB3DBCE_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_13D466AD80D8C83342C9C69C8DB3468D" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_AFFF19999FCEEE1B58EAC69C8DB3DBCE_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TypeOfRestructuringDomain" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_AFFF19999FCEEE1B58EAC69C8DB3DBCE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_13D466AD80D8C83342C9C69C8DB3468D" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_AFFF19999FCEEE1B58EAC69C8DB3DBCE" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_SeveranceAndRelatedCostsMember" xlink:label="loc_pnr_SeveranceAndRelatedCostsMember_75608A69EBABD61271EAC69C8DB46C6F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_AFFF19999FCEEE1B58EAC69C8DB3DBCE" xlink:to="loc_pnr_SeveranceAndRelatedCostsMember_75608A69EBABD61271EAC69C8DB46C6F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_9010945C2DD2A04885E9C69C8DB4D282" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_A400F5E11BC54C39B893C69C8DB42EB0" xlink:to="loc_us-gaap_RestructuringCharges_9010945C2DD2A04885E9C69C8DB4D282" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/Revenue" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenueAdditionalInformationDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenueGeographicNetSalesInformationBySegmentDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueLineItems" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_D74DFE68C2C151FE94856E1AFBAE3965" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DisaggregationOfRevenueTable" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_FA5838FAB46B532D889AFFAE391FD324" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D74DFE68C2C151FE94856E1AFBAE3965" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_FA5838FAB46B532D889AFFAE391FD324" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="loc_srt_StatementGeographicalAxis_202A17827C945D86A586117645BBFFC6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_FA5838FAB46B532D889AFFAE391FD324" xlink:to="loc_srt_StatementGeographicalAxis_202A17827C945D86A586117645BBFFC6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_23AE43A90AF7ACA1331DD7C9A736F455_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_202A17827C945D86A586117645BBFFC6" xlink:to="loc_srt_SegmentGeographicalDomain_23AE43A90AF7ACA1331DD7C9A736F455_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_202A17827C945D86A586117645BBFFC6" xlink:to="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:type="arc" />
    <link:loc xlink:href="https://xbrl.sec.gov/country/2017/country-2017-01-31.xsd#country_US" xlink:label="loc_country_US_54642A057CE85BA780B8527A77B324F8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:to="loc_country_US_54642A057CE85BA780B8527A77B324F8" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_WesternEuropeMember" xlink:label="loc_pnr_WesternEuropeMember_249A3D6176BB5168AC282F60971BDE8E" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:to="loc_pnr_WesternEuropeMember_249A3D6176BB5168AC282F60971BDE8E" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_DevelopingCountriesMember" xlink:label="loc_pnr_DevelopingCountriesMember_8A0033104DA85CC88BA63817EDCB811A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:to="loc_pnr_DevelopingCountriesMember_8A0033104DA85CC88BA63817EDCB811A" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_OtherDevelopedCountriesMember" xlink:label="loc_pnr_OtherDevelopedCountriesMember_86341C65B07E54AC9705184F2129140B" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_88B2A58F72875D11893955C69B3C3A03" xlink:to="loc_pnr_OtherDevelopedCountriesMember_86341C65B07E54AC9705184F2129140B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesByIndustryAxis" xlink:label="loc_us-gaap_EquitySecuritiesByIndustryAxis_DD2DB4F1DD7E5C3BA77F25AF55DA763C" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_FA5838FAB46B532D889AFFAE391FD324" xlink:to="loc_us-gaap_EquitySecuritiesByIndustryAxis_DD2DB4F1DD7E5C3BA77F25AF55DA763C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="loc_us-gaap_EquitySecuritiesIndustryMember_AA77FF07715E0DDDFBFED7C9A737DA71_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquitySecuritiesByIndustryAxis_DD2DB4F1DD7E5C3BA77F25AF55DA763C" xlink:to="loc_us-gaap_EquitySecuritiesIndustryMember_AA77FF07715E0DDDFBFED7C9A737DA71_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_EquitySecuritiesIndustryMember" xlink:label="loc_us-gaap_EquitySecuritiesIndustryMember_DE5E50D267B650AC80C79F6A04D08A42" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquitySecuritiesByIndustryAxis_DD2DB4F1DD7E5C3BA77F25AF55DA763C" xlink:to="loc_us-gaap_EquitySecuritiesIndustryMember_DE5E50D267B650AC80C79F6A04D08A42" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_ResidentialSectorMember" xlink:label="loc_pnr_ResidentialSectorMember_29F5A8F72148510DAA71BC2DEBA3DD0E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_DE5E50D267B650AC80C79F6A04D08A42" xlink:to="loc_pnr_ResidentialSectorMember_29F5A8F72148510DAA71BC2DEBA3DD0E" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_CommercialSectorMember" xlink:label="loc_pnr_CommercialSectorMember_2CD5609E36415F8B9871E79004B8F69B" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_DE5E50D267B650AC80C79F6A04D08A42" xlink:to="loc_pnr_CommercialSectorMember_2CD5609E36415F8B9871E79004B8F69B" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_IndustrialSectorMember" xlink:label="loc_pnr_IndustrialSectorMember_DE4F944D9D1F5C8384710B8EDDABCC93" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_DE5E50D267B650AC80C79F6A04D08A42" xlink:to="loc_pnr_IndustrialSectorMember_DE4F944D9D1F5C8384710B8EDDABCC93" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_3DD567C6CECD53C8AB7429E3E62EB592" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_D74DFE68C2C151FE94856E1AFBAE3965" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_3DD567C6CECD53C8AB7429E3E62EB592" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenuePerformanceObligationsDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_09633E274F425AC1B7B66E1483078988" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_D79956CA31F85E58A9739C7EF3CBC51C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_09633E274F425AC1B7B66E1483078988" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_D79956CA31F85E58A9739C7EF3CBC51C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_11BC48CA044D5C6C9735086C33761034" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_D79956CA31F85E58A9739C7EF3CBC51C" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_11BC48CA044D5C6C9735086C33761034" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceAxis" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3BBF2A2F47165E2DA854E3F99B4F01D0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_D79956CA31F85E58A9739C7EF3CBC51C" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3BBF2A2F47165E2DA854E3F99B4F01D0" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_680A3AC7F9DC3204ECD2D7C9A7CCA9EE_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3BBF2A2F47165E2DA854E3F99B4F01D0" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_680A3AC7F9DC3204ECD2D7C9A7CCA9EE_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_TimingOfTransferOfGoodOrServiceDomain" xlink:label="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_C9FCB09083B553E2A0EC138CDB18E747" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_TimingOfTransferOfGoodOrServiceAxis_3BBF2A2F47165E2DA854E3F99B4F01D0" xlink:to="loc_us-gaap_TimingOfTransferOfGoodOrServiceDomain_C9FCB09083B553E2A0EC138CDB18E747" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeAxis" xlink:label="loc_srt_RangeAxis_E7F6713B2B7450BDBB2F081CF8276D50" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_D79956CA31F85E58A9739C7EF3CBC51C" xlink:to="loc_srt_RangeAxis_E7F6713B2B7450BDBB2F081CF8276D50" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_6F2D599B574159CA45D4D7C9A7CCBB76_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_E7F6713B2B7450BDBB2F081CF8276D50" xlink:to="loc_srt_RangeMember_6F2D599B574159CA45D4D7C9A7CCBB76_F6DE9F3AB2E75C69AA6DC2834080CD35" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_RangeMember" xlink:label="loc_srt_RangeMember_2D098CFA0E885EB78F9A6B3EAFC09561" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_E7F6713B2B7450BDBB2F081CF8276D50" xlink:to="loc_srt_RangeMember_2D098CFA0E885EB78F9A6B3EAFC09561" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MinimumMember" xlink:label="loc_srt_MinimumMember_F7D3DF7B23BC576795B089D15E7384E8" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_2D098CFA0E885EB78F9A6B3EAFC09561" xlink:to="loc_srt_MinimumMember_F7D3DF7B23BC576795B089D15E7384E8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_MaximumMember" xlink:label="loc_srt_MaximumMember_120D64705C1A5244B69B5B2C4BE37AAA" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_2D098CFA0E885EB78F9A6B3EAFC09561" xlink:to="loc_srt_MaximumMember_120D64705C1A5244B69B5B2C4BE37AAA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligation" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_33337DC64E495E948B06612F2790E075" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_09633E274F425AC1B7B66E1483078988" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_33337DC64E495E948B06612F2790E075" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_AE3C2480EE26578B8A40A5A125AD9488" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_09633E274F425AC1B7B66E1483078988" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_AE3C2480EE26578B8A40A5A125AD9488" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenueScheduleOfContractAssetsAndLiabilitiesDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenueTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformationFinancialInformationByReportableSegmentDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_3C9B6EAF712D52567F10BD1297CA4DF6" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4B5E8D531AEEC31C5D16BD1297C84BB1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3C9B6EAF712D52567F10BD1297CA4DF6" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4B5E8D531AEEC31C5D16BD1297C84BB1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_AA4275CBDE167DEAD25DBD1297C9EF82" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_4B5E8D531AEEC31C5D16BD1297C84BB1" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_AA4275CBDE167DEAD25DBD1297C9EF82" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AA4275CBDE167DEAD25DBD1297C9EF82" xlink:to="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_AA4275CBDE167DEAD25DBD1297C9EF82" xlink:to="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_ConsumerSolutionsMember" xlink:label="loc_pnr_ConsumerSolutionsMember_450DE06CC2902F1820F0BD5F2C2E81A7" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:to="loc_pnr_ConsumerSolutionsMember_450DE06CC2902F1820F0BD5F2C2E81A7" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_IndustrialFlowTechnologiesMember" xlink:label="loc_pnr_IndustrialFlowTechnologiesMember_B6FAC7C5A2D9D03516C6BD5F7DDC9F0F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:to="loc_pnr_IndustrialFlowTechnologiesMember_B6FAC7C5A2D9D03516C6BD5F7DDC9F0F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AllOtherSegmentsMember" xlink:label="loc_us-gaap_AllOtherSegmentsMember_6564B36DC42CE56C1DD4BD1297CAB32B" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:to="loc_us-gaap_AllOtherSegmentsMember_6564B36DC42CE56C1DD4BD1297CAB32B" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_84F82AD31731E8DE26D4BD1297CA02FA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F8F8F3010D685C3055E2BD1297C99F6A" xlink:to="loc_us-gaap_OperatingSegmentsMember_84F82AD31731E8DE26D4BD1297CA02FA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_D8621DEC82570796D8DCBD1297CA7E71" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3C9B6EAF712D52567F10BD1297CA4DF6" xlink:to="loc_us-gaap_Revenues_D8621DEC82570796D8DCBD1297CA7E71" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_1E394EA8D981B5A2DD39BD1297CB6CCE" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_3C9B6EAF712D52567F10BD1297CA4DF6" xlink:to="loc_us-gaap_OperatingIncomeLoss_1E394EA8D981B5A2DD39BD1297CB6CCE" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformationReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems" xlink:label="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable" xlink:label="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_4C7B09CAA75DDE2D3C35C69C8BA8DFA1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_4C7B09CAA75DDE2D3C35C69C8BA8DFA1" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StatementOperatingActivitiesSegmentAxis" xlink:label="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_9620D7AB4851A7F6D5CDC69C8BA9316F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_4C7B09CAA75DDE2D3C35C69C8BA8DFA1" xlink:to="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_9620D7AB4851A7F6D5CDC69C8BA9316F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentOperatingActivitiesDomain" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_1DF149FCD237003A1824C69C8BA967BB_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_9620D7AB4851A7F6D5CDC69C8BA9316F" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_1DF149FCD237003A1824C69C8BA967BB_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_SegmentOperatingActivitiesDomain" xlink:label="loc_us-gaap_SegmentOperatingActivitiesDomain_1DF149FCD237003A1824C69C8BA967BB" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementOperatingActivitiesSegmentAxis_9620D7AB4851A7F6D5CDC69C8BA9316F" xlink:to="loc_us-gaap_SegmentOperatingActivitiesDomain_1DF149FCD237003A1824C69C8BA967BB" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaterialReconcilingItemsMember" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_97384AD7C1183A43E58FC69C8BAAB441" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentOperatingActivitiesDomain_1DF149FCD237003A1824C69C8BA967BB" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_97384AD7C1183A43E58FC69C8BAAB441" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsAxis" xlink:label="loc_srt_ConsolidationItemsAxis_81100EC26AC2A4E68DCDC69C8BAA20C5" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_4C7B09CAA75DDE2D3C35C69C8BA8DFA1" xlink:to="loc_srt_ConsolidationItemsAxis_81100EC26AC2A4E68DCDC69C8BAA20C5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_81100EC26AC2A4E68DCDC69C8BAA20C5" xlink:to="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/srt/2019/elts/srt-2019-01-31.xsd#srt_ConsolidationItemsDomain" xlink:label="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_81100EC26AC2A4E68DCDC69C8BAA20C5" xlink:to="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_5B29CEE8B5B44E7293C6C69C8BAADB59" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40" xlink:to="loc_us-gaap_OperatingSegmentsMember_5B29CEE8B5B44E7293C6C69C8BAADB59" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_MaterialReconcilingItemsMember" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_40BAD9241B0A3021AD48C69C8BABC798" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_2E77C4E5EBB12B533F6CC69C8BAA6B40" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_40BAD9241B0A3021AD48C69C8BABC798" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OperatingIncomeLoss" xlink:label="loc_us-gaap_OperatingIncomeLoss_D37DD64BD47848C8DDCEC69C8BABA5DA" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_OperatingIncomeLoss_D37DD64BD47848C8DDCEC69C8BABA5DA" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_Dealrelatedcostsandexpenses" xlink:label="loc_pnr_Dealrelatedcostsandexpenses_0B61C7DBC8D09D53389AC69C8BAB6DC0" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_pnr_Dealrelatedcostsandexpenses_0B61C7DBC8D09D53389AC69C8BAB6DC0" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_InventoryStepUpRelatedToMerger" xlink:label="loc_pnr_InventoryStepUpRelatedToMerger_2776938A9C16DFA73CBCC69C8BAC52B8" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_pnr_InventoryStepUpRelatedToMerger_2776938A9C16DFA73CBCC69C8BAC52B8" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestructuringCharges" xlink:label="loc_us-gaap_RestructuringCharges_19F26867E7DB1C6E5135C69C8BAC6ACA" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_RestructuringCharges_19F26867E7DB1C6E5135C69C8BAC6ACA" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AmortizationOfIntangibleAssets" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_5CD897A635850E7C7D47C69C8BAC6BEE" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_5CD897A635850E7C7D47C69C8BAC6BEE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AssetImpairmentCharges" xlink:label="loc_us-gaap_AssetImpairmentCharges_0DF106E63B8BE5C29BB4C69C8BACCF1C" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_AssetImpairmentCharges_0DF106E63B8BE5C29BB4C69C8BACCF1C" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_GainLossOnSaleOfBusiness" xlink:label="loc_us-gaap_GainLossOnSaleOfBusiness_2343FAC3002B660682A8C69C8BAD0873" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_GainLossOnSaleOfBusiness_2343FAC3002B660682A8C69C8BAD0873" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_COVID19relatedcostsandexpenses" xlink:label="loc_pnr_COVID19relatedcostsandexpenses_DB2A679DCD63E5FC4B27C69C8BAD1C33" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_pnr_COVID19relatedcostsandexpenses_DB2A679DCD63E5FC4B27C69C8BAD1C33" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_InterestRevenueExpenseNet" xlink:label="loc_us-gaap_InterestRevenueExpenseNet_9878F57540FB87492D43C69C8BADA4F7" xlink:type="locator" />
    <link:definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_InterestRevenueExpenseNet_9878F57540FB87492D43C69C8BADA4F7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_OtherExpenses" xlink:label="loc_us-gaap_OtherExpenses_850918BE0E0E8FBE8B48C69C8BAE2212" xlink:type="locator" />
    <link:definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_OtherExpenses_850918BE0E0E8FBE8B48C69C8BAE2212" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_B44B097130A8557FFF0BC69C8BB3E7EA" xlink:type="locator" />
    <link:definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_4E6E3BAE5D18F9823114C69C8BAB71AE" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_B44B097130A8557FFF0BC69C8BB3E7EA" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformationTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlans" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_E789DD0E6F4295CC98B5C69C8DC6751C" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_E789DD0E6F4295CC98B5C69C8DC6751C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_6E476980CF27A1580735C69C8DC64F52" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_E789DD0E6F4295CC98B5C69C8DC6751C" xlink:to="loc_us-gaap_PlanNameAxis_6E476980CF27A1580735C69C8DC64F52" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9098F314C9BE8C50DAF3C69C8DC7D9D3_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_6E476980CF27A1580735C69C8DC64F52" xlink:to="loc_us-gaap_PlanNameDomain_9098F314C9BE8C50DAF3C69C8DC7D9D3_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_9098F314C9BE8C50DAF3C69C8DC7D9D3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_6E476980CF27A1580735C69C8DC64F52" xlink:to="loc_us-gaap_PlanNameDomain_9098F314C9BE8C50DAF3C69C8DC7D9D3" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_TwoThousandTwelveStockIncentivePlanMember" xlink:label="loc_pnr_TwoThousandTwelveStockIncentivePlanMember_FFAD213B6D61B4CC49A0C69C8DC7B8FE" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_9098F314C9BE8C50DAF3C69C8DC7D9D3" xlink:to="loc_pnr_TwoThousandTwelveStockIncentivePlanMember_FFAD213B6D61B4CC49A0C69C8DC7B8FE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_38B1B5F8F941295A3E17C69C8DC7CF78" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_E789DD0E6F4295CC98B5C69C8DC6751C" xlink:to="loc_us-gaap_AwardTypeAxis_38B1B5F8F941295A3E17C69C8DC7CF78" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_38B1B5F8F941295A3E17C69C8DC7CF78" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_38B1B5F8F941295A3E17C69C8DC7CF78" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_A6E96F920C0F5C6EAFE4C69C8DC857E1" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_A6E96F920C0F5C6EAFE4C69C8DC857E1" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockOptionMember" xlink:label="loc_us-gaap_StockOptionMember_F16DF91805A0A6B1C7AEC69C8DC8219F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1" xlink:to="loc_us-gaap_StockOptionMember_F16DF91805A0A6B1C7AEC69C8DC8219F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PerformanceSharesMember" xlink:label="loc_us-gaap_PerformanceSharesMember_260C9AAC3824B51970DFC69C8DC8B935" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_50566412E502847CC8A1C69C8DC82BB1" xlink:to="loc_us-gaap_PerformanceSharesMember_260C9AAC3824B51970DFC69C8DC8B935" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_3C7B51AA97BEA1FC2576C69C8DC9310E" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_3C7B51AA97BEA1FC2576C69C8DC9310E" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_AF537BF0A23BCE197117C69C8DC9229F" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_AF537BF0A23BCE197117C69C8DC9229F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_39A3ED9ECFFD9FC55CBFC69C8DC93904" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_39A3ED9ECFFD9FC55CBFC69C8DC93904" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7239016F17E0CCE52163C69C8DCA5B30" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7239016F17E0CCE52163C69C8DCA5B30" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8FC0C6993AA74E0A0575C69C8DCAC78E" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0158AC5676A2DF74D730C69C8DC94700" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_8FC0C6993AA74E0A0575C69C8DCAC78E" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansScheduleOfShareBasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DEDB23C73AE46F20788EC69C8E1ABCB7" xlink:type="locator" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ABA0702E647F1D1E9C1C69C8E1803A3" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DEDB23C73AE46F20788EC69C8E1ABCB7" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ABA0702E647F1D1E9C1C69C8E1803A3" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_F57495573534C3081D1CC69C8E199119" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_6ABA0702E647F1D1E9C1C69C8E1803A3" xlink:to="loc_us-gaap_AwardTypeAxis_F57495573534C3081D1CC69C8E199119" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_F57495573534C3081D1CC69C8E199119" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_F57495573534C3081D1CC69C8E199119" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_24DA597F657821874DA8C69C8E19AE63" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_24DA597F657821874DA8C69C8E19AE63" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockOptionMember" xlink:label="loc_us-gaap_StockOptionMember_744F670A6A4D70D85381C69C8E1A9AA7" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F" xlink:to="loc_us-gaap_StockOptionMember_744F670A6A4D70D85381C69C8E1A9AA7" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PerformanceSharesMember" xlink:label="loc_us-gaap_PerformanceSharesMember_F5F323AA8D3ABD1B4797C69C8E1AF857" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_C7C5D7FD10D765FDE344C69C8E19373F" xlink:to="loc_us-gaap_PerformanceSharesMember_F5F323AA8D3ABD1B4797C69C8E1AF857" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="loc_us-gaap_ShareBasedCompensation_89627ADF3F583C9450F2C69C8E1B751D" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_DEDB23C73AE46F20788EC69C8E1ABCB7" xlink:to="loc_us-gaap_ShareBasedCompensation_89627ADF3F583C9450F2C69C8E1B751D" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansScheduleOfValuationAssumptionsDetails" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansTables" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/ShareholdersEquity" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/ShareholdersEquityAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:href="pnr-20200331.xsd#pnr_StockholdersEquityNoteDisclosureLineItems" xlink:label="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:type="locator" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_StockholdersEquityNoteDisclosureTable" xlink:label="loc_pnr_StockholdersEquityNoteDisclosureTable_5D6A4005F1B8E2C06D57C69C8BED4546" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_pnr_StockholdersEquityNoteDisclosureTable_5D6A4005F1B8E2C06D57C69C8BED4546" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_FuturedividendsAxis" xlink:label="loc_pnr_FuturedividendsAxis_24E891D83E12BC45EB87C69C8BEEC574" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureTable_5D6A4005F1B8E2C06D57C69C8BED4546" xlink:to="loc_pnr_FuturedividendsAxis_24E891D83E12BC45EB87C69C8BEEC574" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_FuturedividendsDomain" xlink:label="loc_pnr_FuturedividendsDomain_C995EB48CF88486E2410C69C8BEE21C6_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_pnr_FuturedividendsAxis_24E891D83E12BC45EB87C69C8BEEC574" xlink:to="loc_pnr_FuturedividendsDomain_C995EB48CF88486E2410C69C8BEE21C6_default" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_FuturedividendsDomain" xlink:label="loc_pnr_FuturedividendsDomain_C995EB48CF88486E2410C69C8BEE21C6" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_pnr_FuturedividendsAxis_24E891D83E12BC45EB87C69C8BEEC574" xlink:to="loc_pnr_FuturedividendsDomain_C995EB48CF88486E2410C69C8BEE21C6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_40BCC043C8DE1E022BB2C69C8BEECCD6" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureTable_5D6A4005F1B8E2C06D57C69C8BED4546" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_40BCC043C8DE1E022BB2C69C8BEECCD6" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738_default" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_40BCC043C8DE1E022BB2C69C8BEECCD6" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738_default" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_40BCC043C8DE1E022BB2C69C8BEECCD6" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_May2018ShareRepurchaseProgramMember" xlink:label="loc_pnr_May2018ShareRepurchaseProgramMember_FF6F27600B332C581B10C69C8BEF6005" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738" xlink:to="loc_pnr_May2018ShareRepurchaseProgramMember_FF6F27600B332C581B10C69C8BEF6005" xlink:type="arc" />
    <link:loc xlink:href="pnr-20200331.xsd#pnr_December2014ShareRepurchaseProgramMember" xlink:label="loc_pnr_December2014ShareRepurchaseProgramMember_D5FD40178604814BB3DCC69C8BEF0D32" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_90581F5340D3DBADB222C69C8BEF7738" xlink:to="loc_pnr_December2014ShareRepurchaseProgramMember_D5FD40178604814BB3DCC69C8BEF0D32" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_5E9FF96EB549B9502760C69C8BEF1951" xlink:type="locator" />
    <link:definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_5E9FF96EB549B9502760C69C8BEF1951" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramExpirationDate" xlink:label="loc_us-gaap_StockRepurchaseProgramExpirationDate_D0247CDAF2D4E1704813C69C8BF0607D" xlink:type="locator" />
    <link:definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_StockRepurchaseProgramExpirationDate_D0247CDAF2D4E1704813C69C8BF0607D" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodValue" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_F24C9FBEA9FFF9F0E530C69C8BF5231A" xlink:type="locator" />
    <link:definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_F24C9FBEA9FFF9F0E530C69C8BF5231A" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchasedDuringPeriodShares" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_E4755FA610EA38DA9919C69C8BF5A7DE" xlink:type="locator" />
    <link:definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_E4755FA610EA38DA9919C69C8BF5A7DE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_PaymentsForRepurchaseOfCommonStock" xlink:label="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_6270A1DFC1765D58E020C69C8BF6CFD5" xlink:type="locator" />
    <link:definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_PaymentsForRepurchaseOfCommonStock_6270A1DFC1765D58E020C69C8BF6CFD5" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_57194FE0AF8ECEC07918C69C8BF6F471" xlink:type="locator" />
    <link:definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_57194FE0AF8ECEC07918C69C8BF6F471" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_CommonStockDividendsPerShareDeclared" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_BC892E75E1F844DAEE96C69C8BF64EFE" xlink:type="locator" />
    <link:definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_BC892E75E1F844DAEE96C69C8BF64EFE" xlink:type="arc" />
    <link:loc xlink:href="http://xbrl.fasb.org/us-gaap/2019/elts/us-gaap-2019-01-31.xsd#us-gaap_DividendsPayableCurrent" xlink:label="loc_us-gaap_DividendsPayableCurrent_CB7A3A4F36348724B0C8C69C8BF62B0C" xlink:type="locator" />
    <link:definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_D893FE3F1E85532E08CCC69C8BEF5D86" xlink:to="loc_us-gaap_DividendsPayableCurrent_CB7A3A4F36348724B0C8C69C8BF62B0C" xlink:type="arc" />
  </link:definitionLink>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SupplementalBalanceSheetInformation" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SupplementalBalanceSheetInformationDetail" xlink:type="extended" />
  <link:definitionLink xlink:role="http://www.pentair.com/role/SupplementalBalanceSheetInformationTables" xlink:type="extended" />
</link:linkbase>
