<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
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    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001575205</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000937556</issuerCik>
      <issuerName>MASIMO CORP</issuerName>
      <secFileNumber>001-33642</secFileNumber>
      <issuerAddress>
        <com:street1>52 DISCOVERY</com:street1>
        <com:city>IRVINE</com:city>
        <com:stateOrCountry>CA</com:stateOrCountry>
        <com:zipCode>92618</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>949-297-7000</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>McClenahan Thomas Samuel</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Officer</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Charles Schwab &amp; Co., Inc.</name>
        <address>
          <com:street1>3000 Schwab Way,</com:street1>
          <com:city>Westlake</com:city>
          <com:stateOrCountry>TX</com:stateOrCountry>
          <com:zipCode>76262</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>49000</noOfUnitsSold>
      <aggregateMarketValue>9365578.00</aggregateMarketValue>
      <noOfUnitsOutstanding>53948792</noOfUnitsOutstanding>
      <approxSaleDate>03/03/2025</approxSaleDate>
      <securitiesExchangeName>NASDAQ</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>03/03/2025</acquiredDate>
      <natureOfAcquisitionTransaction>Employee Stock Option Exercise</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>MASIMO CORPORATION</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>49000</amountOfSecuritiesAcquired>
      <paymentDate>03/03/2025</paymentDate>
      <natureOfPayment>Broker Payment for Cashless Exercise</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>03/03/2025</noticeDate>
      <signature>Thomas Samuel McClenahan</signature>
    </noticeSignature>
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144
0001575205
XXXXXXXX
LIVE
0000937556
MASIMO CORP
001-33642
52 DISCOVERY
IRVINE
CA
92618
949-297-7000
McClenahan Thomas Samuel
Officer
Common
Charles Schwab & Co., Inc.
3000 Schwab Way,
Westlake
TX
76262
49000
9365578.00
53948792
03/03/2025
NASDAQ
Common
03/03/2025
Employee Stock Option Exercise
MASIMO CORPORATION
N
49000
03/03/2025
Broker Payment for Cashless Exercise
Y
03/03/2025
Thomas Samuel McClenahan