<?xml version="1.0" encoding="UTF-8"?>

<!--XBRL Document Created with the Workiva Platform-->
<!--Copyright 2024 Workiva-->
<!--r:45474eae-5daf-4162-a29f-42766e5cc590,g:f812b1ba-6c6b-403e-91a3-3d197e8145dd-->
<link:linkbase xmlns:link="http://www.xbrl.org/2003/linkbase" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd">
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain"/>
  <link:arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:type="simple" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member"/>
  <link:roleRef roleURI="http://www.pentair.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="simple" xlink:href="pnr-20240930.xsd#CondensedConsolidatedStatementsofChangesinEquity"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/CondensedConsolidatedStatementsofChangesinEquity" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementLineItems_921c5f6b-4f66-40a9-98ef-379f0a52d836" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementTable_79b56e34-c963-40f0-9093-4032bddf6be2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_921c5f6b-4f66-40a9-98ef-379f0a52d836" xlink:to="loc_us-gaap_StatementTable_79b56e34-c963-40f0-9093-4032bddf6be2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_69695162-a368-4da2-992c-4218d41c0699" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementEquityComponentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_79b56e34-c963-40f0-9093-4032bddf6be2" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_69695162-a368-4da2-992c-4218d41c0699" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_69695162-a368-4da2-992c-4218d41c0699_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_69695162-a368-4da2-992c-4218d41c0699" xlink:to="loc_us-gaap_EquityComponentDomain_69695162-a368-4da2-992c-4218d41c0699_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquityComponentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_69695162-a368-4da2-992c-4218d41c0699" xlink:to="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockMember_e1356887-df53-428c-aec0-c67c05c57039" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:to="loc_us-gaap_CommonStockMember_e1356887-df53-428c-aec0-c67c05c57039" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_e1dc3ed0-443e-47e2-a359-52a5659081ea" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdditionalPaidInCapitalMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_e1dc3ed0-443e-47e2-a359-52a5659081ea" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RetainedEarningsMember_b40a3c6b-a1c6-4413-98d9-8031c2b61a89" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RetainedEarningsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:to="loc_us-gaap_RetainedEarningsMember_b40a3c6b-a1c6-4413-98d9-8031c2b61a89" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7d64d41f-e015-47aa-bb49-3d706b6b85fb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_2b324d13-d1f4-4aa3-9c23-7e8377e2c19f" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_7d64d41f-e015-47aa-bb49-3d706b6b85fb" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_22c4898f-97f7-4622-8e53-08b61a68ebac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_921c5f6b-4f66-40a9-98ef-379f0a52d836" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_22c4898f-97f7-4622-8e53-08b61a68ebac" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_921c5f6b-4f66-40a9-98ef-379f0a52d836" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_42bc9eb3-34f3-48ea-8992-242e5d3a3d3d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesOutstanding"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_SharesOutstanding_42bc9eb3-34f3-48ea-8992-242e5d3a3d3d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7b49f41e-5927-4c29-9270-63df7128b22f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7b49f41e-5927-4c29-9270-63df7128b22f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ProfitLoss_fdfee082-89fe-4a57-83df-9d455fdcefdf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ProfitLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_ProfitLoss_fdfee082-89fe-4a57-83df-9d455fdcefdf" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_aab7f2a4-e5a7-46b0-91ce-4caecbcfde5a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_aab7f2a4-e5a7-46b0-91ce-4caecbcfde5a" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsCommonStock_045b471d-0a19-46be-89ee-cb7cc28f9ce7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DividendsCommonStock"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_DividendsCommonStock_045b471d-0a19-46be-89ee-cb7cc28f9ce7" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_fbca0d4e-46f1-42d0-b6ff-6333162a0d07" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_fbca0d4e-46f1-42d0-b6ff-6333162a0d07" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_5bb6d6b0-0289-4287-b387-27f5c6ba8b98" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_5bb6d6b0-0289-4287-b387-27f5c6ba8b98" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_6aca69b8-1ff4-41b9-a050-7d71e2ab43a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_6aca69b8-1ff4-41b9-a050-7d71e2ab43a5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_15e2df81-04de-4428-bb3e-f34ae40c8bd1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_15e2df81-04de-4428-bb3e-f34ae40c8bd1" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_a1f2c9ec-ed30-4ad1-89fb-72dfb4195f37" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardNetOfForfeitures_a1f2c9ec-ed30-4ad1-89fb-72dfb4195f37" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_871f09b6-fdde-4134-8d04-b7d871c2a165" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardNetOfForfeitures_871f09b6-fdde-4134-8d04-b7d871c2a165" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SharesSurrenderedByEmployeesShares_ec712fe1-84b2-44db-8d05-2970b88875e8" xlink:href="pnr-20240930.xsd#pnr_SharesSurrenderedByEmployeesShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_pnr_SharesSurrenderedByEmployeesShares_ec712fe1-84b2-44db-8d05-2970b88875e8" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SharesSurrenderedByEmployees_9f3c1d55-11dd-44d0-aff6-9257b6d2df7c" xlink:href="pnr-20240930.xsd#pnr_SharesSurrenderedByEmployees"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_pnr_SharesSurrenderedByEmployees_9f3c1d55-11dd-44d0-aff6-9257b6d2df7c" xlink:type="arc" order="13"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_59dee98c-5290-4245-a938-9f42d3b2bc00" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_4e58fc2e-f94c-4deb-bef4-e6d2a3f515ce" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_59dee98c-5290-4245-a938-9f42d3b2bc00" xlink:type="arc" order="14"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SharesOutstanding_1adb321d-d378-4960-9f4e-2f193b18fb6e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SharesOutstanding"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_341a5dbf-3969-4ffb-b294-a5c0d8f0b574" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/RevenueGeographicNetSalesInformationbySegmentDetails" xlink:type="simple" xlink:href="pnr-20240930.xsd#RevenueGeographicNetSalesInformationbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenueGeographicNetSalesInformationbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueLineItems_9c23d583-b189-4ccc-ad2d-a5f2a828f907" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DisaggregationOfRevenueTable_f51bfb84-62e3-4ea4-aab5-b1e6fdf084aa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DisaggregationOfRevenueTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_9c23d583-b189-4ccc-ad2d-a5f2a828f907" xlink:to="loc_us-gaap_DisaggregationOfRevenueTable_f51bfb84-62e3-4ea4-aab5-b1e6fdf084aa" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StatementGeographicalAxis_10384295-2ddc-4fe9-ae2f-16ab6c4720e2" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StatementGeographicalAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f51bfb84-62e3-4ea4-aab5-b1e6fdf084aa" xlink:to="loc_srt_StatementGeographicalAxis_10384295-2ddc-4fe9-ae2f-16ab6c4720e2" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_10384295-2ddc-4fe9-ae2f-16ab6c4720e2_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_StatementGeographicalAxis_10384295-2ddc-4fe9-ae2f-16ab6c4720e2" xlink:to="loc_srt_SegmentGeographicalDomain_10384295-2ddc-4fe9-ae2f-16ab6c4720e2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_SegmentGeographicalDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_StatementGeographicalAxis_10384295-2ddc-4fe9-ae2f-16ab6c4720e2" xlink:to="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_country_US_4f032926-225b-482b-9fbc-1c5d53fbf191" xlink:href="https://xbrl.sec.gov/country/2024/country-2024.xsd#country_US"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:to="loc_country_US_4f032926-225b-482b-9fbc-1c5d53fbf191" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_WesternEuropeMember_9693fcf4-07ad-4118-99bd-e3bfe943eba1" xlink:href="pnr-20240930.xsd#pnr_WesternEuropeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:to="loc_pnr_WesternEuropeMember_9693fcf4-07ad-4118-99bd-e3bfe943eba1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DevelopingCountriesMember_63806d3b-f276-4da8-9294-4569fdf04c19" xlink:href="pnr-20240930.xsd#pnr_DevelopingCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:to="loc_pnr_DevelopingCountriesMember_63806d3b-f276-4da8-9294-4569fdf04c19" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_OtherDevelopedCountriesMember_85c9e81a-cc79-4338-a245-0114e08f4e28" xlink:href="pnr-20240930.xsd#pnr_OtherDevelopedCountriesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_SegmentGeographicalDomain_aa4c6073-a0fe-4e92-a17c-7b4f2db80aff" xlink:to="loc_pnr_OtherDevelopedCountriesMember_85c9e81a-cc79-4338-a245-0114e08f4e28" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesByIndustryAxis_34a81075-3d97-4db8-ba92-91655816755f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesByIndustryAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DisaggregationOfRevenueTable_f51bfb84-62e3-4ea4-aab5-b1e6fdf084aa" xlink:to="loc_us-gaap_EquitySecuritiesByIndustryAxis_34a81075-3d97-4db8-ba92-91655816755f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesIndustryMember_34a81075-3d97-4db8-ba92-91655816755f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesIndustryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_EquitySecuritiesByIndustryAxis_34a81075-3d97-4db8-ba92-91655816755f" xlink:to="loc_us-gaap_EquitySecuritiesIndustryMember_34a81075-3d97-4db8-ba92-91655816755f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EquitySecuritiesIndustryMember_36302934-6ce9-4ed5-bcae-a6779621dd48" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EquitySecuritiesIndustryMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_EquitySecuritiesByIndustryAxis_34a81075-3d97-4db8-ba92-91655816755f" xlink:to="loc_us-gaap_EquitySecuritiesIndustryMember_36302934-6ce9-4ed5-bcae-a6779621dd48" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_ResidentialSectorMember_a6a45bad-34c3-41d1-9101-18b59e3b6a6d" xlink:href="pnr-20240930.xsd#pnr_ResidentialSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_36302934-6ce9-4ed5-bcae-a6779621dd48" xlink:to="loc_pnr_ResidentialSectorMember_a6a45bad-34c3-41d1-9101-18b59e3b6a6d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_CommercialSectorMember_ce3921cb-43a0-44f0-b6c7-03b107d1d16a" xlink:href="pnr-20240930.xsd#pnr_CommercialSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_36302934-6ce9-4ed5-bcae-a6779621dd48" xlink:to="loc_pnr_CommercialSectorMember_ce3921cb-43a0-44f0-b6c7-03b107d1d16a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_IndustrialSectorMember_97a9c39f-2306-4a23-a59f-5e0ac11c6602" xlink:href="pnr-20240930.xsd#pnr_IndustrialSectorMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquitySecuritiesIndustryMember_36302934-6ce9-4ed5-bcae-a6779621dd48" xlink:to="loc_pnr_IndustrialSectorMember_97a9c39f-2306-4a23-a59f-5e0ac11c6602" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a46d8fc4-e8b6-4ce4-942e-bde8e6fdae2f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisaggregationOfRevenueLineItems_9c23d583-b189-4ccc-ad2d-a5f2a828f907" xlink:to="loc_us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_a46d8fc4-e8b6-4ce4-942e-bde8e6fdae2f" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/RevenuePerformanceObligationsDetails" xlink:type="simple" xlink:href="pnr-20240930.xsd#RevenuePerformanceObligationsDetails"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenuePerformanceObligationsDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f3945f3e-5e8b-4436-ac1b-288c04fd642c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_f3945f3e-5e8b-4436-ac1b-288c04fd642c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:to="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_28f9e8f6-8e5d-485f-9706-249ec157ec7e_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:to="loc_srt_RangeMember_28f9e8f6-8e5d-485f-9706-249ec157ec7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:to="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_4e245295-dc06-4e00-843c-b8883d7f1dad" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:to="loc_srt_MinimumMember_4e245295-dc06-4e00-843c-b8883d7f1dad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ed8189b3-f6de-4466-bd1a-9862cb722e2b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:to="loc_srt_MaximumMember_ed8189b3-f6de-4466-bd1a-9862cb722e2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_61d0794c-c265-4a9e-b17c-d973c76d0636" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_61d0794c-c265-4a9e-b17c-d973c76d0636" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_eead08bc-e39d-4495-8301-6f75cedef3b4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_eead08bc-e39d-4495-8301-6f75cedef3b4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/RevenuePerformanceObligationsDetails_1" xlink:type="simple" xlink:href="pnr-20240930.xsd#RevenuePerformanceObligationsDetails_1"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RevenuePerformanceObligationsDetails_1" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionTable_a8ac73ef-015f-44c6-9ca6-4c1365cde04d" xlink:to="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_28f9e8f6-8e5d-485f-9706-249ec157ec7e_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:to="loc_srt_RangeMember_28f9e8f6-8e5d-485f-9706-249ec157ec7e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_28f9e8f6-8e5d-485f-9706-249ec157ec7e" xlink:to="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_4e245295-dc06-4e00-843c-b8883d7f1dad" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:to="loc_srt_MinimumMember_4e245295-dc06-4e00-843c-b8883d7f1dad" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_ed8189b3-f6de-4466-bd1a-9862cb722e2b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_c29a1022-0f6c-4fa5-96fb-a17d148d4d93" xlink:to="loc_srt_MaximumMember_ed8189b3-f6de-4466-bd1a-9862cb722e2b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligation_61d0794c-c265-4a9e-b17c-d973c76d0636" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligation_61d0794c-c265-4a9e-b17c-d973c76d0636" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_eead08bc-e39d-4495-8301-6f75cedef3b4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionLineItems_e7e41f47-ce4b-49ac-a57c-561c63673fc7" xlink:to="loc_us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_eead08bc-e39d-4495-8301-6f75cedef3b4" xlink:type="arc" order="1"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansScheduleofSharebasedCompensationExpenseDetails" xlink:type="simple" xlink:href="pnr-20240930.xsd#SharePlansScheduleofSharebasedCompensationExpenseDetails"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansScheduleofSharebasedCompensationExpenseDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_a3a06f27-47ce-40ef-bb5c-531938448bee" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_27f4d965-9823-4a05-a2be-821413ed9b9c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_a3a06f27-47ce-40ef-bb5c-531938448bee" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_27f4d965-9823-4a05-a2be-821413ed9b9c" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_774f3243-540f-46e3-a19f-b3be2125d81c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_27f4d965-9823-4a05-a2be-821413ed9b9c" xlink:to="loc_us-gaap_AwardTypeAxis_774f3243-540f-46e3-a19f-b3be2125d81c" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_774f3243-540f-46e3-a19f-b3be2125d81c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_774f3243-540f-46e3-a19f-b3be2125d81c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_774f3243-540f-46e3-a19f-b3be2125d81c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_59eb0b23-20ae-48c7-86ab-05ecbae4e37d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_774f3243-540f-46e3-a19f-b3be2125d81c" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_59eb0b23-20ae-48c7-86ab-05ecbae4e37d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_ed852180-c548-4910-b149-8202413bb49a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_59eb0b23-20ae-48c7-86ab-05ecbae4e37d" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_ed852180-c548-4910-b149-8202413bb49a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockOptionMember_8d6368fa-7ca3-4989-845f-fad627428c66" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_59eb0b23-20ae-48c7-86ab-05ecbae4e37d" xlink:to="loc_us-gaap_StockOptionMember_8d6368fa-7ca3-4989-845f-fad627428c66" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_08119da4-82dd-46cd-b732-8e8f049c74e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_59eb0b23-20ae-48c7-86ab-05ecbae4e37d" xlink:to="loc_us-gaap_PerformanceSharesMember_08119da4-82dd-46cd-b732-8e8f049c74e6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensation_52174983-af55-4380-b213-73895f38c672" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensation"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_a3a06f27-47ce-40ef-bb5c-531938448bee" xlink:to="loc_us-gaap_ShareBasedCompensation_52174983-af55-4380-b213-73895f38c672" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/SharePlansAdditionalInformationDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#SharePlansAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SharePlansAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3783d87d-9179-40fc-bb41-2ee7f82257e6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3783d87d-9179-40fc-bb41-2ee7f82257e6" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameAxis_dcffc02d-fab1-4d60-8005-1081d8a6b6d9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3783d87d-9179-40fc-bb41-2ee7f82257e6" xlink:to="loc_us-gaap_PlanNameAxis_dcffc02d-fab1-4d60-8005-1081d8a6b6d9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_dcffc02d-fab1-4d60-8005-1081d8a6b6d9_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_dcffc02d-fab1-4d60-8005-1081d8a6b6d9" xlink:to="loc_us-gaap_PlanNameDomain_dcffc02d-fab1-4d60-8005-1081d8a6b6d9_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PlanNameDomain_8c871edb-51c8-4c81-ab26-bcc531bcae7b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_dcffc02d-fab1-4d60-8005-1081d8a6b6d9" xlink:to="loc_us-gaap_PlanNameDomain_8c871edb-51c8-4c81-ab26-bcc531bcae7b" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TwoThousandTwentyShareAndIncentivePlanMember_8eb9ae60-77a2-4ad4-aa85-23af1b13381d" xlink:href="pnr-20240930.xsd#pnr_TwoThousandTwentyShareAndIncentivePlanMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_8c871edb-51c8-4c81-ab26-bcc531bcae7b" xlink:to="loc_pnr_TwoThousandTwentyShareAndIncentivePlanMember_8eb9ae60-77a2-4ad4-aa85-23af1b13381d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AwardTypeAxis_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AwardTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_3783d87d-9179-40fc-bb41-2ee7f82257e6" xlink:to="loc_us-gaap_AwardTypeAxis_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e98a1db5-b652-4e48-889e-216f238d0f11" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_e36ce9ee-bfe8-45b5-a2bd-fc7c38c356ba" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e98a1db5-b652-4e48-889e-216f238d0f11" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember_467bd8b8-fc31-40be-ad09-d6f7072a80ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e98a1db5-b652-4e48-889e-216f238d0f11" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember_467bd8b8-fc31-40be-ad09-d6f7072a80ff" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockOptionMember_ffdc8285-bb80-4d0c-b4e3-6671ea6471bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e98a1db5-b652-4e48-889e-216f238d0f11" xlink:to="loc_us-gaap_StockOptionMember_ffdc8285-bb80-4d0c-b4e3-6671ea6471bd" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember_2a9d2d8c-9625-41d4-aeff-dd1b7157415e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_e98a1db5-b652-4e48-889e-216f238d0f11" xlink:to="loc_us-gaap_PerformanceSharesMember_2a9d2d8c-9625-41d4-aeff-dd1b7157415e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_9a4f1d1a-3c5a-4280-9bf1-eaf3086836d3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesIssuedInPeriod_9a4f1d1a-3c5a-4280-9bf1-eaf3086836d3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0fee9f4b-faac-497c-aa20-a6db2c1f69a6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_0fee9f4b-faac-497c-aa20-a6db2c1f69a6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_52e2cca9-5c05-4ef6-a3dd-0961a780c667" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_52e2cca9-5c05-4ef6-a3dd-0961a780c667" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_45982655-895b-4cf3-a0cf-e629f00ef5a9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_45982655-895b-4cf3-a0cf-e629f00ef5a9" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ce47b8b-9b43-44a5-b9f9-812d0d09b82f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_f04b89e9-6564-429d-a7f9-988d0ad242f1" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_7ce47b8b-9b43-44a5-b9f9-812d0d09b82f" xlink:type="arc" order="4"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringandTransformationProgramCostsIncludedinSellingGeneralAdministrativeExpensesDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#RestructuringandTransformationProgramCostsIncludedinSellingGeneralAdministrativeExpensesDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringandTransformationProgramCostsIncludedinSellingGeneralAdministrativeExpensesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_5fd13516-dfcc-4862-96fa-21ba3f6b3480" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_d58181d3-09c7-4b96-80d7-8df921e680a2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5fd13516-dfcc-4862-96fa-21ba3f6b3480" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_d58181d3-09c7-4b96-80d7-8df921e680a2" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveAxis_cbdd23b5-3223-4fce-bba3-9e19fbf271b1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_d58181d3-09c7-4b96-80d7-8df921e680a2" xlink:to="loc_us-gaap_RestructuringCostAndReserveAxis_cbdd23b5-3223-4fce-bba3-9e19fbf271b1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_cbdd23b5-3223-4fce-bba3-9e19fbf271b1_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_cbdd23b5-3223-4fce-bba3-9e19fbf271b1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_cbdd23b5-3223-4fce-bba3-9e19fbf271b1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TypeOfRestructuringDomain_af5a91b8-cff9-442b-9849-44ec5cbabacb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TypeOfRestructuringDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RestructuringCostAndReserveAxis_cbdd23b5-3223-4fce-bba3-9e19fbf271b1" xlink:to="loc_us-gaap_TypeOfRestructuringDomain_af5a91b8-cff9-442b-9849-44ec5cbabacb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SeveranceAndRelatedCostsMember_bcae6ab3-21d5-4c68-802d-07abc7e83a49" xlink:href="pnr-20240930.xsd#pnr_SeveranceAndRelatedCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_af5a91b8-cff9-442b-9849-44ec5cbabacb" xlink:to="loc_pnr_SeveranceAndRelatedCostsMember_bcae6ab3-21d5-4c68-802d-07abc7e83a49" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherRestructuringMember_319eaefa-be94-4876-811d-7799b62a3e81" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherRestructuringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_TypeOfRestructuringDomain_af5a91b8-cff9-442b-9849-44ec5cbabacb" xlink:to="loc_us-gaap_OtherRestructuringMember_319eaefa-be94-4876-811d-7799b62a3e81" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TransformationTypeAxis_08d21585-73cd-431d-b259-9ac7bd90447f" xlink:href="pnr-20240930.xsd#pnr_TransformationTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_d58181d3-09c7-4b96-80d7-8df921e680a2" xlink:to="loc_pnr_TransformationTypeAxis_08d21585-73cd-431d-b259-9ac7bd90447f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TransformationTypeDomain_08d21585-73cd-431d-b259-9ac7bd90447f_default" xlink:href="pnr-20240930.xsd#pnr_TransformationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_pnr_TransformationTypeAxis_08d21585-73cd-431d-b259-9ac7bd90447f" xlink:to="loc_pnr_TransformationTypeDomain_08d21585-73cd-431d-b259-9ac7bd90447f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TransformationTypeDomain_63f6cba2-a53f-4355-b138-54c705553cb5" xlink:href="pnr-20240930.xsd#pnr_TransformationTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_pnr_TransformationTypeAxis_08d21585-73cd-431d-b259-9ac7bd90447f" xlink:to="loc_pnr_TransformationTypeDomain_63f6cba2-a53f-4355-b138-54c705553cb5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SeveranceAndRelatedCostsMember_55e09fbf-6828-4aa3-a7a2-a73a12860b78" xlink:href="pnr-20240930.xsd#pnr_SeveranceAndRelatedCostsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_TransformationTypeDomain_63f6cba2-a53f-4355-b138-54c705553cb5" xlink:to="loc_pnr_SeveranceAndRelatedCostsMember_55e09fbf-6828-4aa3-a7a2-a73a12860b78" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_OtherTransformationMember_8c3de52a-32be-4def-8487-bce4984bdde1" xlink:href="pnr-20240930.xsd#pnr_OtherTransformationMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_TransformationTypeDomain_63f6cba2-a53f-4355-b138-54c705553cb5" xlink:to="loc_pnr_OtherTransformationMember_8c3de52a-32be-4def-8487-bce4984bdde1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCharges_aaf9c346-f2f1-453b-ba78-c5f053ebbb40" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5fd13516-dfcc-4862-96fa-21ba3f6b3480" xlink:to="loc_us-gaap_RestructuringCharges_aaf9c346-f2f1-453b-ba78-c5f053ebbb40" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TransformationCosts_1ed797da-4d41-4bdb-9cda-c7c5da82d1ae" xlink:href="pnr-20240930.xsd#pnr_TransformationCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5fd13516-dfcc-4862-96fa-21ba3f6b3480" xlink:to="loc_pnr_TransformationCosts_1ed797da-4d41-4bdb-9cda-c7c5da82d1ae" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TotalRestructuringAndTransformationCosts_02221032-c926-4bb4-8273-457ac659b209" xlink:href="pnr-20240930.xsd#pnr_TotalRestructuringAndTransformationCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5fd13516-dfcc-4862-96fa-21ba3f6b3480" xlink:to="loc_pnr_TotalRestructuringAndTransformationCosts_02221032-c926-4bb4-8273-457ac659b209" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/RestructuringandTransformationProgramRestructuringCostsbySegmentDetails" xlink:type="simple" xlink:href="pnr-20240930.xsd#RestructuringandTransformationProgramRestructuringCostsbySegmentDetails"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/RestructuringandTransformationProgramRestructuringCostsbySegmentDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestructuringCostAndReserveLineItems_5a70a0b8-8af7-460e-808d-3625990ece3c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestructuringCostAndReserveLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24254a22-82e4-49b0-b83e-8e6fbfed95b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfRestructuringAndRelatedCostsTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5a70a0b8-8af7-460e-808d-3625990ece3c" xlink:to="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24254a22-82e4-49b0-b83e-8e6fbfed95b7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_cef5641e-1368-4553-9d55-0e0131f6a7ab" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRestructuringAndRelatedCostsTable_24254a22-82e4-49b0-b83e-8e6fbfed95b7" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_cef5641e-1368-4553-9d55-0e0131f6a7ab" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_cef5641e-1368-4553-9d55-0e0131f6a7ab_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_cef5641e-1368-4553-9d55-0e0131f6a7ab" xlink:to="loc_us-gaap_SegmentDomain_cef5641e-1368-4553-9d55-0e0131f6a7ab_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_cef5641e-1368-4553-9d55-0e0131f6a7ab" xlink:to="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_IndustrialFlowTechnologiesMember_ef638ec9-8766-4cdf-bf0e-8c2460bae76f" xlink:href="pnr-20240930.xsd#pnr_IndustrialFlowTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:to="loc_pnr_IndustrialFlowTechnologiesMember_ef638ec9-8766-4cdf-bf0e-8c2460bae76f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_WaterSolutionsSegmentMember_e00c79ac-45ce-466a-b779-9da713821225" xlink:href="pnr-20240930.xsd#pnr_WaterSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:to="loc_pnr_WaterSolutionsSegmentMember_e00c79ac-45ce-466a-b779-9da713821225" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PoolSegmentMember_def8419b-2788-4c68-ac5a-58826840dca4" xlink:href="pnr-20240930.xsd#pnr_PoolSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:to="loc_pnr_PoolSegmentMember_def8419b-2788-4c68-ac5a-58826840dca4" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_CorporateAndOtherNonsegmentMember_65e23cd2-b835-4775-890e-159c1a68b028" xlink:href="pnr-20240930.xsd#pnr_CorporateAndOtherNonsegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:to="loc_pnr_CorporateAndOtherNonsegmentMember_65e23cd2-b835-4775-890e-159c1a68b028" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_FlowSegmentMember_b50e7a68-c45a-47ed-b412-c3705265ad20" xlink:href="pnr-20240930.xsd#pnr_FlowSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_fe8593d2-6244-4c2a-8173-0845b22a842d" xlink:to="loc_pnr_FlowSegmentMember_b50e7a68-c45a-47ed-b412-c3705265ad20" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TotalRestructuringAndTransformationCosts_bb51d749-c656-4b61-a050-060d545d1b4b" xlink:href="pnr-20240930.xsd#pnr_TotalRestructuringAndTransformationCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RestructuringCostAndReserveLineItems_5a70a0b8-8af7-460e-808d-3625990ece3c" xlink:to="loc_pnr_TotalRestructuringAndTransformationCosts_bb51d749-c656-4b61-a050-060d545d1b4b" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillandOtherIdentifiableIntangibleAssetsChangesinCarryingAmountofGoodwillbySegmentDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#GoodwillandOtherIdentifiableIntangibleAssetsChangesinCarryingAmountofGoodwillbySegmentDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillandOtherIdentifiableIntangibleAssetsChangesinCarryingAmountofGoodwillbySegmentDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillLineItems_6c9a6e39-2053-42dc-9652-b18886c614bd" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfGoodwillTable_5bd83aba-20ef-42fc-81e6-4f7a3c0136f0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfGoodwillTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_GoodwillLineItems_6c9a6e39-2053-42dc-9652-b18886c614bd" xlink:to="loc_us-gaap_ScheduleOfGoodwillTable_5bd83aba-20ef-42fc-81e6-4f7a3c0136f0" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_577725ab-5f5a-4df0-a49a-5fbd5284fbcf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfGoodwillTable_5bd83aba-20ef-42fc-81e6-4f7a3c0136f0" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_577725ab-5f5a-4df0-a49a-5fbd5284fbcf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_577725ab-5f5a-4df0-a49a-5fbd5284fbcf_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_577725ab-5f5a-4df0-a49a-5fbd5284fbcf" xlink:to="loc_us-gaap_SegmentDomain_577725ab-5f5a-4df0-a49a-5fbd5284fbcf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_577725ab-5f5a-4df0-a49a-5fbd5284fbcf" xlink:to="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_IndustrialFlowTechnologiesMember_32d85d5c-df6b-4ef7-926f-45a232d2ddec" xlink:href="pnr-20240930.xsd#pnr_IndustrialFlowTechnologiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:to="loc_pnr_IndustrialFlowTechnologiesMember_32d85d5c-df6b-4ef7-926f-45a232d2ddec" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_WaterSolutionsSegmentMember_7dd14f6b-067b-4b43-9262-f2ac4c268502" xlink:href="pnr-20240930.xsd#pnr_WaterSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:to="loc_pnr_WaterSolutionsSegmentMember_7dd14f6b-067b-4b43-9262-f2ac4c268502" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PoolSegmentMember_f8c2d0a4-d81b-47fb-afcc-aeef233ec44c" xlink:href="pnr-20240930.xsd#pnr_PoolSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:to="loc_pnr_PoolSegmentMember_f8c2d0a4-d81b-47fb-afcc-aeef233ec44c" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_FlowSegmentMember_75941da0-3bd1-4a33-bd21-76daf4e0f141" xlink:href="pnr-20240930.xsd#pnr_FlowSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_e29bfb79-e330-41b9-b9c9-e6438f22a595" xlink:to="loc_pnr_FlowSegmentMember_75941da0-3bd1-4a33-bd21-76daf4e0f141" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillRollForward_b839ce92-1142-4cc6-b3ff-6676f6c7ad7b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillRollForward"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillLineItems_6c9a6e39-2053-42dc-9652-b18886c614bd" xlink:to="loc_us-gaap_GoodwillRollForward_b839ce92-1142-4cc6-b3ff-6676f6c7ad7b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_3ebedb76-43cc-492f-9fb5-04dba18b76b7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_b839ce92-1142-4cc6-b3ff-6676f6c7ad7b" xlink:to="loc_us-gaap_Goodwill_3ebedb76-43cc-492f-9fb5-04dba18b76b7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_GoodwillOtherIncreaseDecrease_defc3163-1575-446a-b231-671180195d1b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_GoodwillOtherIncreaseDecrease"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_GoodwillRollForward_b839ce92-1142-4cc6-b3ff-6676f6c7ad7b" xlink:to="loc_us-gaap_GoodwillOtherIncreaseDecrease_defc3163-1575-446a-b231-671180195d1b" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Goodwill_ab53b8d8-41cb-439f-9007-c1a878dbe168" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Goodwill"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/GoodwillandOtherIdentifiableIntangibleAssetsDetailofIdentifiableIntangibleAssetsDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#GoodwillandOtherIdentifiableIntangibleAssetsDetailofIdentifiableIntangibleAssetsDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/GoodwillandOtherIdentifiableIntangibleAssetsDetailofIdentifiableIntangibleAssetsDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:href="pnr-20240930.xsd#pnr_AcquiredIntangibleAssetsByMajorClassLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_c27538de-fc4e-45ba-9dad-ca0c1611cf2b" xlink:href="pnr-20240930.xsd#pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_c27538de-fc4e-45ba-9dad-ca0c1611cf2b" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_974def8c-fc01-423b-970c-bae1c880c3b5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_pnr_ScheduleOfAcquiredIntangibleAssetsByMajorClassTable_c27538de-fc4e-45ba-9dad-ca0c1611cf2b" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_974def8c-fc01-423b-970c-bae1c880c3b5" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_974def8c-fc01-423b-970c-bae1c880c3b5_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_974def8c-fc01-423b-970c-bae1c880c3b5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_974def8c-fc01-423b-970c-bae1c880c3b5_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9a836dbb-8d55-489c-a2cd-24b79669b0c6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis_974def8c-fc01-423b-970c-bae1c880c3b5" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9a836dbb-8d55-489c-a2cd-24b79669b0c6" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CustomerRelationshipsMember_047a7392-4871-4fef-9eb9-f29af87b74e4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CustomerRelationshipsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9a836dbb-8d55-489c-a2cd-24b79669b0c6" xlink:to="loc_us-gaap_CustomerRelationshipsMember_047a7392-4871-4fef-9eb9-f29af87b74e4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PatentedTechnologyMember_59db1eda-c28e-4cae-a857-5a6aa327bf8a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PatentedTechnologyMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9a836dbb-8d55-489c-a2cd-24b79669b0c6" xlink:to="loc_us-gaap_PatentedTechnologyMember_59db1eda-c28e-4cae-a857-5a6aa327bf8a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TradeNamesMember_98465d72-430d-49da-9601-6bf1848f6bc0" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TradeNamesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FiniteLivedIntangibleAssetsMajorClassNameDomain_9a836dbb-8d55-489c-a2cd-24b79669b0c6" xlink:to="loc_us-gaap_TradeNamesMember_98465d72-430d-49da-9601-6bf1848f6bc0" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsGross_81f3f30f-5e70-4797-ab79-e92d43d777b9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsGross"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsGross_81f3f30f-5e70-4797-ab79-e92d43d777b9" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_5dc0e8df-e718-4b24-b97a-690cff06ad53" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization_5dc0e8df-e718-4b24-b97a-690cff06ad53" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c205e471-8e78-42b7-b86f-5c2b40c2a813" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FiniteLivedIntangibleAssetsNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_FiniteLivedIntangibleAssetsNet_c205e471-8e78-42b7-b86f-5c2b40c2a813" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_c429cb1d-d641-4dcf-bfa9-1449234d710b" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_IndefiniteLivedIntangibleAssetsExcludingGoodwill_c429cb1d-d641-4dcf-bfa9-1449234d710b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_92b58a83-33cc-4e54-bfd8-96b7d29f0c57" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntangibleAssetsGrossExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_IntangibleAssetsGrossExcludingGoodwill_92b58a83-33cc-4e54-bfd8-96b7d29f0c57" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_2001c32e-fe48-485e-9249-4d33781b6259" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IntangibleAssetsNetExcludingGoodwill"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_AcquiredIntangibleAssetsByMajorClassLineItems_ce9ed39f-9e45-43a6-8ff6-fcc7dbbf26d6" xlink:to="loc_us-gaap_IntangibleAssetsNetExcludingGoodwill_2001c32e-fe48-485e-9249-4d33781b6259" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/DebtDebtandAverageInterestRatesonDebtOutstandingDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#DebtDebtandAverageInterestRatesonDebtOutstandingDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtDebtandAverageInterestRatesonDebtOutstandingDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_1a3a4075-c5e4-4711-9c3a-6e6afa29e9a3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:to="loc_us-gaap_DebtInstrumentTable_1a3a4075-c5e4-4711-9c3a-6e6afa29e9a3" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_ff44ec1e-c131-4c5c-855a-62bfed2ee70f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a3a4075-c5e4-4711-9c3a-6e6afa29e9a3" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_ff44ec1e-c131-4c5c-855a-62bfed2ee70f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_ff44ec1e-c131-4c5c-855a-62bfed2ee70f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ff44ec1e-c131-4c5c-855a-62bfed2ee70f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_ff44ec1e-c131-4c5c-855a-62bfed2ee70f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_a32292fa-a1bc-4a5c-ad29-d883912b3040" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_ff44ec1e-c131-4c5c-855a-62bfed2ee70f" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_a32292fa-a1bc-4a5c-ad29-d883912b3040" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_ddeaa7de-c541-4825-8fd1-607a85ca8e6e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a32292fa-a1bc-4a5c-ad29-d883912b3040" xlink:to="loc_us-gaap_LineOfCreditMember_ddeaa7de-c541-4825-8fd1-607a85ca8e6e" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TermLoansMember_2bbac632-b82a-490f-a041-7b538f680047" xlink:href="pnr-20240930.xsd#pnr_TermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a32292fa-a1bc-4a5c-ad29-d883912b3040" xlink:to="loc_pnr_TermLoansMember_2bbac632-b82a-490f-a041-7b538f680047" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SeniorNotesMember_60e593d8-fb69-4114-8ace-17d47bec0886" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SeniorNotesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_a32292fa-a1bc-4a5c-ad29-d883912b3040" xlink:to="loc_us-gaap_SeniorNotesMember_60e593d8-fb69-4114-8ace-17d47bec0886" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_da441268-0bfc-47e0-b89f-521b05782ed6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a3a4075-c5e4-4711-9c3a-6e6afa29e9a3" xlink:to="loc_us-gaap_CreditFacilityAxis_da441268-0bfc-47e0-b89f-521b05782ed6" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_da441268-0bfc-47e0-b89f-521b05782ed6_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_da441268-0bfc-47e0-b89f-521b05782ed6" xlink:to="loc_us-gaap_CreditFacilityDomain_da441268-0bfc-47e0-b89f-521b05782ed6_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_3d6f3b09-568b-45c7-837f-3691837989be" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_da441268-0bfc-47e0-b89f-521b05782ed6" xlink:to="loc_us-gaap_CreditFacilityDomain_3d6f3b09-568b-45c7-837f-3691837989be" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_ef63841e-b008-4631-8520-92f4b806ff68" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_3d6f3b09-568b-45c7-837f-3691837989be" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_ef63841e-b008-4631-8520-92f4b806ff68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_01c967fe-6647-420e-a00b-00e31b2a963c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_1a3a4075-c5e4-4711-9c3a-6e6afa29e9a3" xlink:to="loc_us-gaap_DebtInstrumentAxis_01c967fe-6647-420e-a00b-00e31b2a963c" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_01c967fe-6647-420e-a00b-00e31b2a963c_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_01c967fe-6647-420e-a00b-00e31b2a963c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_01c967fe-6647-420e-a00b-00e31b2a963c_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_01c967fe-6647-420e-a00b-00e31b2a963c" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_A5YearTermLoanFacilityMember_e7540022-6f9b-4486-b550-53020b1d986b" xlink:href="pnr-20240930.xsd#pnr_A5YearTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:to="loc_pnr_A5YearTermLoanFacilityMember_e7540022-6f9b-4486-b550-53020b1d986b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TermLoans1033DueIn2024Member_19105d0b-6d3e-4398-9374-f4c3cb6fe868" xlink:href="pnr-20240930.xsd#pnr_TermLoans1033DueIn2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:to="loc_pnr_TermLoans1033DueIn2024Member_19105d0b-6d3e-4398-9374-f4c3cb6fe868" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember_52f3a824-6c55-4ecf-8978-957ca5088cf1" xlink:href="pnr-20240930.xsd#pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:to="loc_pnr_SeniorNotesFourPointSixFivePercentDueTwentyTwentyFiveMember_52f3a824-6c55-4ecf-8978-957ca5088cf1" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SeniorNotes4500Due2029Member_f171ac96-9744-4aa4-9afd-7bc2508de378" xlink:href="pnr-20240930.xsd#pnr_SeniorNotes4500Due2029Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:to="loc_pnr_SeniorNotes4500Due2029Member_f171ac96-9744-4aa4-9afd-7bc2508de378" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_SeniorNotesFivePointNinePercentDueTwentyThirtyTwoMember_a5e4084a-b353-46ba-820f-ff957fa30d83" xlink:href="pnr-20240930.xsd#pnr_SeniorNotesFivePointNinePercentDueTwentyThirtyTwoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_ee381271-0d66-455d-8705-f3e68938f943" xlink:to="loc_pnr_SeniorNotesFivePointNinePercentDueTwentyThirtyTwoMember_a5e4084a-b353-46ba-820f-ff957fa30d83" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtWeightedAverageInterestRate_c86aa714-a53d-47a4-a647-f1912994d58a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtWeightedAverageInterestRate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:to="loc_us-gaap_DebtWeightedAverageInterestRate_c86aa714-a53d-47a4-a647-f1912994d58a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_6fd779dd-2fc6-4bd9-8768-17ee2dd93ef7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_6fd779dd-2fc6-4bd9-8768-17ee2dd93ef7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnamortizedDebtIssuanceExpense_ad588801-cd4d-46d1-a89e-ae5879c61629" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnamortizedDebtIssuanceExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:to="loc_us-gaap_UnamortizedDebtIssuanceExpense_ad588801-cd4d-46d1-a89e-ae5879c61629" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_463bd6e0-7ed5-4508-8b22-70e2030695cc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtLongtermAndShorttermCombinedAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_7d127a39-dd88-43c3-8415-89bbf04b364a" xlink:to="loc_us-gaap_DebtLongtermAndShorttermCombinedAmount_463bd6e0-7ed5-4508-8b22-70e2030695cc" xlink:type="arc" order="3"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/DebtAdditionalInformationDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#DebtAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DebtAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityAxis_8378acfa-85ad-4199-b278-dfec1c36b30f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_us-gaap_LineOfCreditFacilityAxis_8378acfa-85ad-4199-b278-dfec1c36b30f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_8378acfa-85ad-4199-b278-dfec1c36b30f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_8378acfa-85ad-4199-b278-dfec1c36b30f" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_8378acfa-85ad-4199-b278-dfec1c36b30f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityLenderDomain_8fcab10a-1db6-4651-829d-6d5aa1743774" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityLenderDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LineOfCreditFacilityAxis_8378acfa-85ad-4199-b278-dfec1c36b30f" xlink:to="loc_us-gaap_LineOfCreditFacilityLenderDomain_8fcab10a-1db6-4651-829d-6d5aa1743774" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_OtherCreditFacilitiesMember_32140f2b-1f57-4264-837b-c5f14ad1e947" xlink:href="pnr-20240930.xsd#pnr_OtherCreditFacilitiesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLenderDomain_8fcab10a-1db6-4651-829d-6d5aa1743774" xlink:to="loc_pnr_OtherCreditFacilitiesMember_32140f2b-1f57-4264-837b-c5f14ad1e947" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeAxis_f11e03ef-11b4-4132-8cf1-2e3484ae3f14" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_us-gaap_LongtermDebtTypeAxis_f11e03ef-11b4-4132-8cf1-2e3484ae3f14" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_f11e03ef-11b4-4132-8cf1-2e3484ae3f14_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f11e03ef-11b4-4132-8cf1-2e3484ae3f14" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_f11e03ef-11b4-4132-8cf1-2e3484ae3f14_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtTypeDomain_441db07b-b6f2-404a-9bf4-203bf9d291a8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LongtermDebtTypeAxis_f11e03ef-11b4-4132-8cf1-2e3484ae3f14" xlink:to="loc_us-gaap_LongtermDebtTypeDomain_441db07b-b6f2-404a-9bf4-203bf9d291a8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditMember_653a3f95-2132-4f1c-88bb-0236c5c08119" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_441db07b-b6f2-404a-9bf4-203bf9d291a8" xlink:to="loc_us-gaap_LineOfCreditMember_653a3f95-2132-4f1c-88bb-0236c5c08119" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TermLoansMember_f22037ab-8aa7-4228-a98c-8e19b757ebd1" xlink:href="pnr-20240930.xsd#pnr_TermLoansMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_441db07b-b6f2-404a-9bf4-203bf9d291a8" xlink:to="loc_pnr_TermLoansMember_f22037ab-8aa7-4228-a98c-8e19b757ebd1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_UnsecuredDebtMember_4faed107-6438-4f85-8492-b50b55c4b5ac" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_UnsecuredDebtMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LongtermDebtTypeDomain_441db07b-b6f2-404a-9bf4-203bf9d291a8" xlink:to="loc_us-gaap_UnsecuredDebtMember_4faed107-6438-4f85-8492-b50b55c4b5ac" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityAxis_978b2bf6-02b5-47ab-a489-5eff8b51edd2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_us-gaap_CreditFacilityAxis_978b2bf6-02b5-47ab-a489-5eff8b51edd2" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_978b2bf6-02b5-47ab-a489-5eff8b51edd2_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_978b2bf6-02b5-47ab-a489-5eff8b51edd2" xlink:to="loc_us-gaap_CreditFacilityDomain_978b2bf6-02b5-47ab-a489-5eff8b51edd2_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CreditFacilityDomain_250814c6-fc10-4c50-a093-2821393807e7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CreditFacilityDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_978b2bf6-02b5-47ab-a489-5eff8b51edd2" xlink:to="loc_us-gaap_CreditFacilityDomain_250814c6-fc10-4c50-a093-2821393807e7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_67bde212-1fd9-4109-8fdf-a4f66c0e6ec4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RevolvingCreditFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_250814c6-fc10-4c50-a093-2821393807e7" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_67bde212-1fd9-4109-8fdf-a4f66c0e6ec4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeAxis_9d3434b6-eff3-4c6c-ab90-4b5c35947e08" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_srt_RangeAxis_9d3434b6-eff3-4c6c-ab90-4b5c35947e08" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_9d3434b6-eff3-4c6c-ab90-4b5c35947e08_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_RangeAxis_9d3434b6-eff3-4c6c-ab90-4b5c35947e08" xlink:to="loc_srt_RangeMember_9d3434b6-eff3-4c6c-ab90-4b5c35947e08_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RangeMember_590cc601-7d55-4e91-b9a1-ca43848823ad" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RangeMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_RangeAxis_9d3434b6-eff3-4c6c-ab90-4b5c35947e08" xlink:to="loc_srt_RangeMember_590cc601-7d55-4e91-b9a1-ca43848823ad" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MinimumMember_a6f1f16a-7c61-4cc3-a772-4ce81806c396" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MinimumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_590cc601-7d55-4e91-b9a1-ca43848823ad" xlink:to="loc_srt_MinimumMember_a6f1f16a-7c61-4cc3-a772-4ce81806c396" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_MaximumMember_f00b7495-b6fd-4d82-829a-061eec9c2765" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_MaximumMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RangeMember_590cc601-7d55-4e91-b9a1-ca43848823ad" xlink:to="loc_srt_MaximumMember_f00b7495-b6fd-4d82-829a-061eec9c2765" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentAxis_08d39dda-6ccc-4954-ba6f-585dfe18b57e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_us-gaap_DebtInstrumentAxis_08d39dda-6ccc-4954-ba6f-585dfe18b57e" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_08d39dda-6ccc-4954-ba6f-585dfe18b57e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DebtInstrumentAxis_08d39dda-6ccc-4954-ba6f-585dfe18b57e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_08d39dda-6ccc-4954-ba6f-585dfe18b57e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentNameDomain_d79afdde-6401-41c8-ab13-a6e39458022f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DebtInstrumentAxis_08d39dda-6ccc-4954-ba6f-585dfe18b57e" xlink:to="loc_us-gaap_DebtInstrumentNameDomain_d79afdde-6401-41c8-ab13-a6e39458022f" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TermLoans1033DueIn2024Member_f4a459d1-452d-4681-8f9c-e6679611fc68" xlink:href="pnr-20240930.xsd#pnr_TermLoans1033DueIn2024Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d79afdde-6401-41c8-ab13-a6e39458022f" xlink:to="loc_pnr_TermLoans1033DueIn2024Member_f4a459d1-452d-4681-8f9c-e6679611fc68" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TermLoansDue2023Member_9c2349e4-8883-4a13-a7a5-269da2aa62a0" xlink:href="pnr-20240930.xsd#pnr_TermLoansDue2023Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d79afdde-6401-41c8-ab13-a6e39458022f" xlink:to="loc_pnr_TermLoansDue2023Member_9c2349e4-8883-4a13-a7a5-269da2aa62a0" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_A5YearTermLoanFacilityMember_0968b3d2-cb94-438c-af6f-9a7640fabfcd" xlink:href="pnr-20240930.xsd#pnr_A5YearTermLoanFacilityMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentNameDomain_d79afdde-6401-41c8-ab13-a6e39458022f" xlink:to="loc_pnr_A5YearTermLoanFacilityMember_0968b3d2-cb94-438c-af6f-9a7640fabfcd" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_CounterpartyNameAxis_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_CounterpartyNameAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DebtInstrumentTable_69246eef-1f70-4b2b-9059-62636530ac23" xlink:to="loc_srt_CounterpartyNameAxis_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_CounterpartyNameAxis_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_RepurchaseAgreementCounterpartyNameDomain_53d27977-2d35-4cf3-9fc3-457aed693086" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_RepurchaseAgreementCounterpartyNameDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_CounterpartyNameAxis_2d9fcb8c-0bd0-4676-b3a7-4d6d0439cc46" xlink:to="loc_srt_RepurchaseAgreementCounterpartyNameDomain_53d27977-2d35-4cf3-9fc3-457aed693086" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PentairPentairFinanceSRlPFSAMember_2e3ac147-cfda-4d33-82b5-b740bd71ef3f" xlink:href="pnr-20240930.xsd#pnr_PentairPentairFinanceSRlPFSAMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_RepurchaseAgreementCounterpartyNameDomain_53d27977-2d35-4cf3-9fc3-457aed693086" xlink:to="loc_pnr_PentairPentairFinanceSRlPFSAMember_2e3ac147-cfda-4d33-82b5-b740bd71ef3f" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_a58d455c-78ee-47bf-9521-bfca9172dfcf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_a58d455c-78ee-47bf-9521-bfca9172dfcf" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RepaymentsOfLongTermDebt_d81060bf-4d5f-411a-9a7a-4bc7914c79f9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RepaymentsOfLongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_RepaymentsOfLongTermDebt_d81060bf-4d5f-411a-9a7a-4bc7914c79f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_a8880c17-ee29-4b23-9875-62177311cf0e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity_a8880c17-ee29-4b23-9875-62177311cf0e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit_28c4fd15-9277-455a-9f08-5e9925c05c36" xlink:href="pnr-20240930.xsd#pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_LineofCreditFacilityAccordionFeatureIncreaseLimit_28c4fd15-9277-455a-9f08-5e9925c05c36" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_b00716da-d22a-4427-ad50-1e7328fa9769" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentFaceAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_b00716da-d22a-4427-ad50-1e7328fa9769" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentPeriodicPayment_f9a5faad-995d-4724-8aab-e6838e89b92f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentPeriodicPayment"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_DebtInstrumentPeriodicPayment_f9a5faad-995d-4724-8aab-e6838e89b92f" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DebtInstrumentCarryingAmount_86aca65e-1180-4f46-a273-7966e8dbf0a5" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DebtInstrumentCarryingAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_DebtInstrumentCarryingAmount_86aca65e-1180-4f46-a273-7966e8dbf0a5" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DebtInstrumentCovenantUnrestrictedCash_1715389e-c9d3-4fb7-986e-fbfe64a02cd2" xlink:href="pnr-20240930.xsd#pnr_DebtInstrumentCovenantUnrestrictedCash"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_DebtInstrumentCovenantUnrestrictedCash_1715389e-c9d3-4fb7-986e-fbfe64a02cd2" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DebtInstrumentLeverageRatioCovenant_2e2a56ab-2d66-436d-b8e7-f6306b51dcc5" xlink:href="pnr-20240930.xsd#pnr_DebtInstrumentLeverageRatioCovenant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_DebtInstrumentLeverageRatioCovenant_2e2a56ab-2d66-436d-b8e7-f6306b51dcc5" xlink:type="arc" order="8"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DebtInstrumentLeverageRatioCovenantPeriod_3236e1a6-9d95-40c8-a9a4-ad91ce0a229f" xlink:href="pnr-20240930.xsd#pnr_DebtInstrumentLeverageRatioCovenantPeriod"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_DebtInstrumentLeverageRatioCovenantPeriod_3236e1a6-9d95-40c8-a9a4-ad91ce0a229f" xlink:type="arc" order="9"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DebtInstrumentCovenantNumberOfTestingPeriods_3cc394f1-6880-4b60-a30c-72e4d0e21fb0" xlink:href="pnr-20240930.xsd#pnr_DebtInstrumentCovenantNumberOfTestingPeriods"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_DebtInstrumentCovenantNumberOfTestingPeriods_3cc394f1-6880-4b60-a30c-72e4d0e21fb0" xlink:type="arc" order="10"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DebtInstrumentEBITDARatioCovenant_490fac85-45d8-4c8a-a2e3-584cc73cb2b7" xlink:href="pnr-20240930.xsd#pnr_DebtInstrumentEBITDARatioCovenant"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_pnr_DebtInstrumentEBITDARatioCovenant_490fac85-45d8-4c8a-a2e3-584cc73cb2b7" xlink:type="arc" order="11"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LineOfCredit_403d177d-3d7a-4fdd-bf0e-88d66cc8f33c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LineOfCredit"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_LineOfCredit_403d177d-3d7a-4fdd-bf0e-88d66cc8f33c" xlink:type="arc" order="12"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_fdbf019f-d3a4-4589-bc29-3438f7e07dc6" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DebtInstrumentLineItems_db9c4383-54fe-445d-b6ab-8c0e15976b21" xlink:to="loc_us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextRollingTwelveMonths_fdbf019f-d3a4-4589-bc29-3438f7e07dc6" xlink:type="arc" order="13"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesandFinancialInstrumentsAdditionalInformationDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#DerivativesandFinancialInstrumentsAdditionalInformationDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesandFinancialInstrumentsAdditionalInformationDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_8925880f-215e-441e-b760-f700d5921500" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_DerivativeTable_8925880f-215e-441e-b760-f700d5921500" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_c03f5861-45f2-4230-ac36-3b6ef674a4c8" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_8925880f-215e-441e-b760-f700d5921500" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_c03f5861-45f2-4230-ac36-3b6ef674a4c8" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_c03f5861-45f2-4230-ac36-3b6ef674a4c8_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_c03f5861-45f2-4230-ac36-3b6ef674a4c8" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_c03f5861-45f2-4230-ac36-3b6ef674a4c8_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_c03f5861-45f2-4230-ac36-3b6ef674a4c8" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignExchangeContractMember_a3fd918d-d231-4108-a14c-71d41e88e785" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignExchangeContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:to="loc_us-gaap_ForeignExchangeContractMember_a3fd918d-d231-4108-a14c-71d41e88e785" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CurrencySwapMember_612cc99b-017e-4930-a44b-15bf635fa448" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CurrencySwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:to="loc_us-gaap_CurrencySwapMember_612cc99b-017e-4930-a44b-15bf635fa448" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateSwapMember_b4f8e138-2b6d-4fdc-976e-8228e2d09b77" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateSwapMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:to="loc_us-gaap_InterestRateSwapMember_b4f8e138-2b6d-4fdc-976e-8228e2d09b77" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_InterestRateCollarMember_10048738-ab03-4706-9864-1126e5adf158" xlink:href="pnr-20240930.xsd#pnr_InterestRateCollarMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_fa2ce520-90a2-45d5-bf8e-d70f0c6f86d1" xlink:to="loc_pnr_InterestRateCollarMember_10048738-ab03-4706-9864-1126e5adf158" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeNotionalAmount_7dd648a6-9322-4438-be9c-ed1fc7c8fea3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeNotionalAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_DerivativeNotionalAmount_7dd648a6-9322-4438-be9c-ed1fc7c8fea3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax_94eaee61-9d46-479e-9e91-f6bd7ff93489" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_TranslationAdjustmentForNetInvestmentHedgeIncreaseDecreaseNetOfTax_94eaee61-9d46-479e-9e91-f6bd7ff93489" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PaymentsForHedgeInvestingActivities_5a688138-b316-4d3c-8c13-2afdbd99b516" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PaymentsForHedgeInvestingActivities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_PaymentsForHedgeInvestingActivities_5a688138-b316-4d3c-8c13-2afdbd99b516" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_NetPaymentsForHedge_53f21ebd-353a-463d-9637-ade1e1c56697" xlink:href="pnr-20240930.xsd#pnr_NetPaymentsForHedge"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_pnr_NetPaymentsForHedge_53f21ebd-353a-463d-9637-ade1e1c56697" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeOperating_991ee58c-d397-407e-a97f-68deddf9fbf4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestIncomeOperating"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_InterestIncomeOperating_991ee58c-d397-407e-a97f-68deddf9fbf4" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax_47646ca8-8fd6-47c1-9c96-c759d4d2c53c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_d862588f-911f-43a0-ace0-fe5d6349857c" xlink:to="loc_us-gaap_AociLossCashFlowHedgeCumulativeGainLossAfterTax_47646ca8-8fd6-47c1-9c96-c759d4d2c53c" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesandFinancialInstrumentsRecordedAmountsandEstimatedFairValuesDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#DerivativesandFinancialInstrumentsRecordedAmountsandEstimatedFairValuesDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesandFinancialInstrumentsRecordedAmountsandEstimatedFairValuesDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLineItems_fe7e8808-8f50-416c-87ab-7a5de99eaa7e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeTable_673090e9-0f68-4c96-9912-4fc45763c609" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_DerivativeLineItems_fe7e8808-8f50-416c-87ab-7a5de99eaa7e" xlink:to="loc_us-gaap_DerivativeTable_673090e9-0f68-4c96-9912-4fc45763c609" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementBasisAxis_967f65f1-5410-4615-8447-bd9b30b0d1ff" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementBasisAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_DerivativeTable_673090e9-0f68-4c96-9912-4fc45763c609" xlink:to="loc_us-gaap_FairValueByMeasurementBasisAxis_967f65f1-5410-4615-8447-bd9b30b0d1ff" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_967f65f1-5410-4615-8447-bd9b30b0d1ff_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_967f65f1-5410-4615-8447-bd9b30b0d1ff" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_967f65f1-5410-4615-8447-bd9b30b0d1ff_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1b49b4ca-f918-402f-8ade-ccc1fe4e9366" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueDisclosureItemAmountsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementBasisAxis_967f65f1-5410-4615-8447-bd9b30b0d1ff" xlink:to="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1b49b4ca-f918-402f-8ade-ccc1fe4e9366" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1c9b9b3e-0ef0-4674-b813-9922013f4adc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PortionAtFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1b49b4ca-f918-402f-8ade-ccc1fe4e9366" xlink:to="loc_us-gaap_PortionAtFairValueFairValueDisclosureMember_1c9b9b3e-0ef0-4674-b813-9922013f4adc" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_018898ba-2738-4e38-a055-1607f98f0ad9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CarryingReportedAmountFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1b49b4ca-f918-402f-8ade-ccc1fe4e9366" xlink:to="loc_us-gaap_CarryingReportedAmountFairValueDisclosureMember_018898ba-2738-4e38-a055-1607f98f0ad9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_7473af0d-1e66-4839-955c-a57c549084db" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_EstimateOfFairValueFairValueDisclosureMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueDisclosureItemAmountsDomain_1b49b4ca-f918-402f-8ade-ccc1fe4e9366" xlink:to="loc_us-gaap_EstimateOfFairValueFairValueDisclosureMember_7473af0d-1e66-4839-955c-a57c549084db" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtPercentageBearingVariableInterestAmount_9776e68f-6423-451b-be15-79c676ca6a4d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtPercentageBearingVariableInterestAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_fe7e8808-8f50-416c-87ab-7a5de99eaa7e" xlink:to="loc_us-gaap_LongtermDebtPercentageBearingVariableInterestAmount_9776e68f-6423-451b-be15-79c676ca6a4d" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongtermDebtPercentageBearingFixedInterestAmount_9404d42a-b388-4b0c-9010-d8b0a5341b33" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongtermDebtPercentageBearingFixedInterestAmount"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_fe7e8808-8f50-416c-87ab-7a5de99eaa7e" xlink:to="loc_us-gaap_LongtermDebtPercentageBearingFixedInterestAmount_9404d42a-b388-4b0c-9010-d8b0a5341b33" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_LongTermDebt_129ec256-9d79-4549-98a7-a9805b08d38e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_LongTermDebt"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeLineItems_fe7e8808-8f50-416c-87ab-7a5de99eaa7e" xlink:to="loc_us-gaap_LongTermDebt_129ec256-9d79-4549-98a7-a9805b08d38e" xlink:type="arc" order="2"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/DerivativesandFinancialInstrumentsAssetsandLiabilitiesMeasuredatFairValueDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#DerivativesandFinancialInstrumentsAssetsandLiabilitiesMeasuredatFairValueDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/DerivativesandFinancialInstrumentsAssetsandLiabilitiesMeasuredatFairValueDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e4fd2cd2-559f-4062-8fac-717ea77f4875" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e4fd2cd2-559f-4062-8fac-717ea77f4875" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_09eb96af-ac0f-42d8-8069-68d10183bc4e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e4fd2cd2-559f-4062-8fac-717ea77f4875" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_09eb96af-ac0f-42d8-8069-68d10183bc4e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_09eb96af-ac0f-42d8-8069-68d10183bc4e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_09eb96af-ac0f-42d8-8069-68d10183bc4e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_09eb96af-ac0f-42d8-8069-68d10183bc4e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_09eb96af-ac0f-42d8-8069-68d10183bc4e" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_d322796f-69c6-4bd8-a4eb-2d82d0b4d56a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel1Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_d322796f-69c6-4bd8-a4eb-2d82d0b4d56a" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_1193fa63-0177-4a8c-9f49-d510078460bb" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel2Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_1193fa63-0177-4a8c-9f49-d510078460bb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueInputsLevel3Member_a0bbf1c5-304f-4db0-9995-364fe1ff999e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueInputsLevel3Member"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:to="loc_us-gaap_FairValueInputsLevel3Member_a0bbf1c5-304f-4db0-9995-364fe1ff999e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_4d4e35c2-9d1b-428c-be4e-2d776a3eb700" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_b16721be-3848-4eb2-b0aa-5af6db12e422" xlink:to="loc_us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember_4d4e35c2-9d1b-428c-be4e-2d776a3eb700" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueByMeasurementFrequencyAxis_35dcccff-a699-4b83-8378-f296e330e47f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueByMeasurementFrequencyAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e4fd2cd2-559f-4062-8fac-717ea77f4875" xlink:to="loc_us-gaap_FairValueByMeasurementFrequencyAxis_35dcccff-a699-4b83-8378-f296e330e47f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_35dcccff-a699-4b83-8378-f296e330e47f_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_35dcccff-a699-4b83-8378-f296e330e47f" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_35dcccff-a699-4b83-8378-f296e330e47f_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementFrequencyDomain_ae1bcda0-1977-4044-8625-677b9b220565" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementFrequencyDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByMeasurementFrequencyAxis_35dcccff-a699-4b83-8378-f296e330e47f" xlink:to="loc_us-gaap_FairValueMeasurementFrequencyDomain_ae1bcda0-1977-4044-8625-677b9b220565" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_FairValueMeasurementsRecurringMember_53360a33-07b5-4497-a968-d94fbee049f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_FairValueMeasurementsRecurringMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementFrequencyDomain_ae1bcda0-1977-4044-8625-677b9b220565" xlink:to="loc_us-gaap_FairValueMeasurementsRecurringMember_53360a33-07b5-4497-a968-d94fbee049f3" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeInstrumentRiskAxis_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeInstrumentRiskAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisTable_e4fd2cd2-559f-4062-8fac-717ea77f4875" xlink:to="loc_us-gaap_DerivativeInstrumentRiskAxis_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeContractTypeDomain_5d3ca88f-b690-42ff-9cd8-b001d9f39a56" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeContractTypeDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_DerivativeInstrumentRiskAxis_5fc907d8-65cd-43a9-bf90-b6cdcdc54ccc" xlink:to="loc_us-gaap_DerivativeContractTypeDomain_5d3ca88f-b690-42ff-9cd8-b001d9f39a56" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestRateContractMember_2c7b9bbe-d299-4d84-9677-2b0e7f978c4c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestRateContractMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DerivativeContractTypeDomain_5d3ca88f-b690-42ff-9cd8-b001d9f39a56" xlink:to="loc_us-gaap_InterestRateContractMember_2c7b9bbe-d299-4d84-9677-2b0e7f978c4c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssets_14f091c7-1170-42f3-afbe-d96327e5eef2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_DerivativeAssets_14f091c7-1170-42f3-afbe-d96327e5eef2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeLiabilities_f8062578-d9d4-46e7-bafe-e130719baaaf" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeLiabilities"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_DerivativeLiabilities_f8062578-d9d4-46e7-bafe-e130719baaaf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_7751eacd-46bb-4ab1-89e2-f8e67acf3628" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyContractAssetFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_ForeignCurrencyContractAssetFairValueDisclosure_7751eacd-46bb-4ab1-89e2-f8e67acf3628" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_d4c2c268-f00c-49db-80be-fba2509152f3" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_ForeignCurrencyContractsLiabilityFairValueDisclosure_d4c2c268-f00c-49db-80be-fba2509152f3" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_DeferredCompensationPlanAssetsFairValueDisclosure_bb1f1255-1464-490d-92cb-a7e1a1da7b47" xlink:href="pnr-20240930.xsd#pnr_DeferredCompensationPlanAssetsFairValueDisclosure"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_pnr_DeferredCompensationPlanAssetsFairValueDisclosure_bb1f1255-1464-490d-92cb-a7e1a1da7b47" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_e42147f9-04d4-4425-8984-0c8cfc54b3a7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_00c35d21-23ba-4ad0-8541-707aacb89827" xlink:to="loc_us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet_e42147f9-04d4-4425-8984-0c8cfc54b3a7" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/ShareholdersEquityDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#ShareholdersEquityDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/ShareholdersEquityDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:href="pnr-20240930.xsd#pnr_StockholdersEquityNoteDisclosureLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_StockholdersEquityNoteDisclosureTable_66c91611-1f23-41ee-9a1e-cf78d9452f82" xlink:href="pnr-20240930.xsd#pnr_StockholdersEquityNoteDisclosureTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_pnr_StockholdersEquityNoteDisclosureTable_66c91611-1f23-41ee-9a1e-cf78d9452f82" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramAxis_49e65b41-f987-4bce-b3c9-d27b615e42cf" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureTable_66c91611-1f23-41ee-9a1e-cf78d9452f82" xlink:to="loc_srt_ShareRepurchaseProgramAxis_49e65b41-f987-4bce-b3c9-d27b615e42cf" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_49e65b41-f987-4bce-b3c9-d27b615e42cf_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ShareRepurchaseProgramAxis_49e65b41-f987-4bce-b3c9-d27b615e42cf" xlink:to="loc_srt_ShareRepurchaseProgramDomain_49e65b41-f987-4bce-b3c9-d27b615e42cf_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ShareRepurchaseProgramDomain_162cfc2e-ebdf-4201-93a3-203c9eeb8b1a" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ShareRepurchaseProgramDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ShareRepurchaseProgramAxis_49e65b41-f987-4bce-b3c9-d27b615e42cf" xlink:to="loc_srt_ShareRepurchaseProgramDomain_162cfc2e-ebdf-4201-93a3-203c9eeb8b1a" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_December2020ShareRepurchaseProgramMember_6b26c32b-5bb0-4a53-be65-5ef5341832c8" xlink:href="pnr-20240930.xsd#pnr_December2020ShareRepurchaseProgramMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ShareRepurchaseProgramDomain_162cfc2e-ebdf-4201-93a3-203c9eeb8b1a" xlink:to="loc_pnr_December2020ShareRepurchaseProgramMember_6b26c32b-5bb0-4a53-be65-5ef5341832c8" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramAuthorizedAmount1_94d835d5-846c-4466-bf72-00a1dabb903b" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramAuthorizedAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_srt_StockRepurchaseProgramAuthorizedAmount1_94d835d5-846c-4466-bf72-00a1dabb903b" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_StockRepurchaseProgramExpirationDate_cc0d7471-0112-4456-8161-c91e71c1fdcb" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_StockRepurchaseProgramExpirationDate"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_srt_StockRepurchaseProgramExpirationDate_cc0d7471-0112-4456-8161-c91e71c1fdcb" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodShares_1aa25df6-b1e9-4ac7-aba7-efb157b12e9f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedDuringPeriodShares"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodShares_1aa25df6-b1e9-4ac7-aba7-efb157b12e9f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_80677a1f-9cbd-4c62-bd83-9b3ce0a68caa" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_80677a1f-9cbd-4c62-bd83-9b3ce0a68caa" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CommonStockDividendsPerShareDeclared_5af24521-fa0d-4aa1-ba42-83aedfde2c0c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CommonStockDividendsPerShareDeclared"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_us-gaap_CommonStockDividendsPerShareDeclared_5af24521-fa0d-4aa1-ba42-83aedfde2c0c" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_DividendsPayableCurrent_7ba3fead-274c-459b-b03b-670bb0fbc503" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_DividendsPayableCurrent"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_us-gaap_DividendsPayableCurrent_7ba3fead-274c-459b-b03b-670bb0fbc503" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockRepurchasedDuringPeriodValue_a60ec516-e730-492b-bc26-d9f5a69d3f5d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockRepurchasedDuringPeriodValue"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_pnr_StockholdersEquityNoteDisclosureLineItems_86cdd8d0-1c5e-4f59-919c-43da7bb76e78" xlink:to="loc_us-gaap_StockRepurchasedDuringPeriodValue_a60ec516-e730-492b-bc26-d9f5a69d3f5d" xlink:type="arc" order="6"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformationFinancialInformationbyReportableSegmentDetail" xlink:type="simple" xlink:href="pnr-20240930.xsd#SegmentInformationFinancialInformationbyReportableSegmentDetail"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformationFinancialInformationbyReportableSegmentDetail" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_d5f006f5-c868-47ee-9c21-38d7efb672e1" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingInformationLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8fadf620-347d-48d7-863b-e9597afd7372" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_d5f006f5-c868-47ee-9c21-38d7efb672e1" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8fadf620-347d-48d7-863b-e9597afd7372" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_3dfbd8c8-826d-4c46-b87f-5516e4a157d7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8fadf620-347d-48d7-863b-e9597afd7372" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_3dfbd8c8-826d-4c46-b87f-5516e4a157d7" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_3dfbd8c8-826d-4c46-b87f-5516e4a157d7_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_3dfbd8c8-826d-4c46-b87f-5516e4a157d7" xlink:to="loc_us-gaap_SegmentDomain_3dfbd8c8-826d-4c46-b87f-5516e4a157d7_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_7b70884f-1c54-4935-9fc8-20d223637176" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_3dfbd8c8-826d-4c46-b87f-5516e4a157d7" xlink:to="loc_us-gaap_SegmentDomain_7b70884f-1c54-4935-9fc8-20d223637176" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_FlowSegmentMember_60f86361-64c3-4cb8-9ca1-4a774055f28c" xlink:href="pnr-20240930.xsd#pnr_FlowSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7b70884f-1c54-4935-9fc8-20d223637176" xlink:to="loc_pnr_FlowSegmentMember_60f86361-64c3-4cb8-9ca1-4a774055f28c" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_WaterSolutionsSegmentMember_423e1a06-606e-41a5-8d5c-98688f6ce102" xlink:href="pnr-20240930.xsd#pnr_WaterSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7b70884f-1c54-4935-9fc8-20d223637176" xlink:to="loc_pnr_WaterSolutionsSegmentMember_423e1a06-606e-41a5-8d5c-98688f6ce102" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PoolSegmentMember_50ce6872-557d-4d2e-b782-1d4f49872dfe" xlink:href="pnr-20240930.xsd#pnr_PoolSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_7b70884f-1c54-4935-9fc8-20d223637176" xlink:to="loc_pnr_PoolSegmentMember_50ce6872-557d-4d2e-b782-1d4f49872dfe" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_fba09d1c-70c5-48d9-be1b-7b97c1bd3962" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_8fadf620-347d-48d7-863b-e9597afd7372" xlink:to="loc_srt_ConsolidationItemsAxis_fba09d1c-70c5-48d9-be1b-7b97c1bd3962" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_fba09d1c-70c5-48d9-be1b-7b97c1bd3962_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_fba09d1c-70c5-48d9-be1b-7b97c1bd3962" xlink:to="loc_srt_ConsolidationItemsDomain_fba09d1c-70c5-48d9-be1b-7b97c1bd3962_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_1f82f931-a34a-486e-8e1e-2f5eeda003f4" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_fba09d1c-70c5-48d9-be1b-7b97c1bd3962" xlink:to="loc_srt_ConsolidationItemsDomain_1f82f931-a34a-486e-8e1e-2f5eeda003f4" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_46f39a02-89af-4406-8332-0d6b31db9cf4" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1f82f931-a34a-486e-8e1e-2f5eeda003f4" xlink:to="loc_us-gaap_OperatingSegmentsMember_46f39a02-89af-4406-8332-0d6b31db9cf4" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_51dfdab1-2418-4be2-a34d-90df7737b610" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_1f82f931-a34a-486e-8e1e-2f5eeda003f4" xlink:to="loc_us-gaap_CorporateNonSegmentMember_51dfdab1-2418-4be2-a34d-90df7737b610" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_Revenues_d401d896-3034-4eb8-b28f-b9d12e31f92a" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_Revenues"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_d5f006f5-c868-47ee-9c21-38d7efb672e1" xlink:to="loc_us-gaap_Revenues_d401d896-3034-4eb8-b28f-b9d12e31f92a" xlink:type="arc" order="0"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://www.pentair.com/role/SegmentInformationReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails" xlink:type="simple" xlink:href="pnr-20240930.xsd#SegmentInformationReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails"/>
  <link:definitionLink xlink:role="http://www.pentair.com/role/SegmentInformationReconciliationofOperatingProfitLossfromSegmentstoConsolidatedDetails" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_03b2b61a-6ed0-476a-b525-0462a6566ae7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_03b2b61a-6ed0-476a-b525-0462a6566ae7" xlink:type="arc" order="1" xbrldt:closed="true" xbrldt:contextElement="segment"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsAxis_b6086b81-b743-4caa-9cc3-c7286ff68bc1" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_03b2b61a-6ed0-476a-b525-0462a6566ae7" xlink:to="loc_srt_ConsolidationItemsAxis_b6086b81-b743-4caa-9cc3-c7286ff68bc1" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_b6086b81-b743-4caa-9cc3-c7286ff68bc1_default" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_srt_ConsolidationItemsAxis_b6086b81-b743-4caa-9cc3-c7286ff68bc1" xlink:to="loc_srt_ConsolidationItemsDomain_b6086b81-b743-4caa-9cc3-c7286ff68bc1_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_srt_ConsolidationItemsDomain_555cacc9-4087-4034-aafb-770c4aff66f9" xlink:href="https://xbrl.fasb.org/srt/2024/elts/srt-2024.xsd#srt_ConsolidationItemsDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_srt_ConsolidationItemsAxis_b6086b81-b743-4caa-9cc3-c7286ff68bc1" xlink:to="loc_srt_ConsolidationItemsDomain_555cacc9-4087-4034-aafb-770c4aff66f9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingSegmentsMember_0376d359-6604-471f-8a7c-660a005a9fa2" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingSegmentsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_555cacc9-4087-4034-aafb-770c4aff66f9" xlink:to="loc_us-gaap_OperatingSegmentsMember_0376d359-6604-471f-8a7c-660a005a9fa2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_CorporateNonSegmentMember_4a7c9313-c7b1-4628-8deb-a83c79c76d6e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_CorporateNonSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_555cacc9-4087-4034-aafb-770c4aff66f9" xlink:to="loc_us-gaap_CorporateNonSegmentMember_4a7c9313-c7b1-4628-8deb-a83c79c76d6e" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_MaterialReconcilingItemsMember_407076af-d93e-43f2-8833-9f9517eb654f" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_MaterialReconcilingItemsMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_srt_ConsolidationItemsDomain_555cacc9-4087-4034-aafb-770c4aff66f9" xlink:to="loc_us-gaap_MaterialReconcilingItemsMember_407076af-d93e-43f2-8833-9f9517eb654f" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_78e8e496-b35d-4262-ae63-0f0dccb9971e" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StatementBusinessSegmentsAxis"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ReconciliationOfOperatingProfitLossFromSegmentsToConsolidatedTable_03b2b61a-6ed0-476a-b525-0462a6566ae7" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_78e8e496-b35d-4262-ae63-0f0dccb9971e" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_78e8e496-b35d-4262-ae63-0f0dccb9971e_default" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_78e8e496-b35d-4262-ae63-0f0dccb9971e" xlink:to="loc_us-gaap_SegmentDomain_78e8e496-b35d-4262-ae63-0f0dccb9971e_default" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_SegmentDomain_a5d20e64-69c3-40de-9a8e-531157615fe9" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_SegmentDomain"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_78e8e496-b35d-4262-ae63-0f0dccb9971e" xlink:to="loc_us-gaap_SegmentDomain_a5d20e64-69c3-40de-9a8e-531157615fe9" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_FlowSegmentMember_0ac168a4-5faf-4787-8f0b-5cd9528194c2" xlink:href="pnr-20240930.xsd#pnr_FlowSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a5d20e64-69c3-40de-9a8e-531157615fe9" xlink:to="loc_pnr_FlowSegmentMember_0ac168a4-5faf-4787-8f0b-5cd9528194c2" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_WaterSolutionsSegmentMember_5ba11043-9313-4cbf-b7b1-9995c6933a40" xlink:href="pnr-20240930.xsd#pnr_WaterSolutionsSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a5d20e64-69c3-40de-9a8e-531157615fe9" xlink:to="loc_pnr_WaterSolutionsSegmentMember_5ba11043-9313-4cbf-b7b1-9995c6933a40" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PoolSegmentMember_f1da6863-befb-4dec-abb4-ed7459383ee9" xlink:href="pnr-20240930.xsd#pnr_PoolSegmentMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_a5d20e64-69c3-40de-9a8e-531157615fe9" xlink:to="loc_pnr_PoolSegmentMember_f1da6863-befb-4dec-abb4-ed7459383ee9" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OperatingIncomeLoss_c0a1e3c5-709f-488c-833b-4d4fa936ffc7" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OperatingIncomeLoss"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_OperatingIncomeLoss_c0a1e3c5-709f-488c-833b-4d4fa936ffc7" xlink:type="arc" order="0"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AssetImpairmentCharges_5107ad56-cdc3-4120-97d3-f4e86f3fe046" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AssetImpairmentCharges"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_AssetImpairmentCharges_5107ad56-cdc3-4120-97d3-f4e86f3fe046" xlink:type="arc" order="1"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_RestructuringandOtherCosts_a62d287a-678e-4ead-aeaa-5117bc489c30" xlink:href="pnr-20240930.xsd#pnr_RestructuringandOtherCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_pnr_RestructuringandOtherCosts_a62d287a-678e-4ead-aeaa-5117bc489c30" xlink:type="arc" order="2"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_TransformationCosts_cd9409b6-0971-4fe5-9604-59293917dd7b" xlink:href="pnr-20240930.xsd#pnr_TransformationCosts"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_pnr_TransformationCosts_cd9409b6-0971-4fe5-9604-59293917dd7b" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_AmortizationOfIntangibleAssets_d6848782-8ad8-4c60-bc41-605352fd9b61" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_AmortizationOfIntangibleAssets"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_AmortizationOfIntangibleAssets_d6848782-8ad8-4c60-bc41-605352fd9b61" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_LegalAccrualAdjustments_cb40217e-e08d-4d83-ab19-1a97557abd40" xlink:href="pnr-20240930.xsd#pnr_LegalAccrualAdjustments"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_pnr_LegalAccrualAdjustments_cb40217e-e08d-4d83-ab19-1a97557abd40" xlink:type="arc" order="5"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_InterestIncomeExpenseNet_2e9ccd1d-8c05-4e50-a451-fe34e2ee625c" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_InterestIncomeExpenseNet"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_InterestIncomeExpenseNet_2e9ccd1d-8c05-4e50-a451-fe34e2ee625c" xlink:type="arc" order="6"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_OtherNonoperatingIncomeExpense_bf306be2-f6eb-4bb5-94d5-e60ec071fbdc" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_OtherNonoperatingIncomeExpense"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_OtherNonoperatingIncomeExpense_bf306be2-f6eb-4bb5-94d5-e60ec071fbdc" xlink:type="arc" order="7"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4a45918e-6e4f-4283-b4d5-e3f8afc6148d" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingReconcilingItemForOperatingProfitLossFromSegmentToConsolidatedLineItems_8d8cd88d-8793-4031-8fba-cadc7893385d" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_4a45918e-6e4f-4283-b4d5-e3f8afc6148d" xlink:type="arc" order="8"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#AwardTypeOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/AwardTypeOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_RestrictedStockUnitsRSUMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_RestrictedStockUnitsRSUMember" xlink:type="arc" order="3"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_StockOptionMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_StockOptionMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_StockOptionMember" xlink:type="arc" order="4"/>
    <link:loc xlink:type="locator" xlink:label="loc_us-gaap_PerformanceSharesMember" xlink:href="https://xbrl.fasb.org/us-gaap/2024/elts/us-gaap-2024.xsd#us-gaap_PerformanceSharesMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="loc_us-gaap_PerformanceSharesMember" xlink:type="arc" order="5"/>
  </link:definitionLink>
  <link:roleRef roleURI="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="simple" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#IndividualsOnly"/>
  <link:definitionLink xlink:role="http://xbrl.sec.gov/ecd/role/IndividualsOnly" xlink:type="extended">
    <link:loc xlink:type="locator" xlink:label="loc_ecd_AllIndividualsMember" xlink:href="https://xbrl.sec.gov/ecd/2024/ecd-2024.xsd#ecd_AllIndividualsMember"/>
    <link:loc xlink:type="locator" xlink:label="loc_pnr_PhilipM.RolchigoMember_95f4d768-9775-4c54-96fa-cc87f758a1bd" xlink:href="pnr-20240930.xsd#pnr_PhilipM.RolchigoMember"/>
    <link:definitionArc xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_ecd_AllIndividualsMember" xlink:to="loc_pnr_PhilipM.RolchigoMember_95f4d768-9775-4c54-96fa-cc87f758a1bd" xlink:type="arc" order="2"/>
  </link:definitionLink>
</link:linkbase>
