<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:com="http://www.sec.gov/edgar/common">
  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001216055</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
      </filer>
      <liveTestFlag>LIVE</liveTestFlag>



    </filerInfo>
  </headerData>
  <formData>
    <issuerInfo>
      <issuerCik>0000097745</issuerCik>
      <issuerName>THERMO FISHER SCIENTIFIC INC.</issuerName>
      <secFileNumber>001-08002</secFileNumber>
      <issuerAddress>
        <com:street1>168 THIRD AVENUE</com:street1>
        <com:city>WALTHAM</com:city>
        <com:stateOrCountry>MA</com:stateOrCountry>
        <com:zipCode>02451</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>7816221000</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>CASPER MARC N</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <relationshipToIssuer>Officer</relationshipToIssuer>
        <relationshipToIssuer>Director</relationshipToIssuer>
      </relationshipsToIssuer>
    </issuerInfo>
    <securitiesInformation>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <brokerOrMarketmakerDetails>
        <name>Fidelity Brokerage Services LLC</name>
        <address>
          <com:street1>900 Salem Street</com:street1>
          <com:city>Smithfield</com:city>
          <com:stateOrCountry>RI</com:stateOrCountry>
          <com:zipCode>02917</com:zipCode>
        </address>
      </brokerOrMarketmakerDetails>
      <noOfUnitsSold>4883</noOfUnitsSold>
      <aggregateMarketValue>2822374.00</aggregateMarketValue>
      <noOfUnitsOutstanding>369747286</noOfUnitsOutstanding>
      <approxSaleDate>08/07/2026</approxSaleDate>
      <securitiesExchangeName>NYSE</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>02/15/2013</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>4608</amountOfSecuritiesAcquired>
      <paymentDate>02/15/2013</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>08/07/2026</acquiredDate>
      <natureOfAcquisitionTransaction>Stock Option Exercise</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>275</amountOfSecuritiesAcquired>
      <paymentDate>08/07/2026</paymentDate>
      <natureOfPayment>Cash</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Floral Park Associates Inc.</name>
        <address>
          <com:street1>168 Third Avenue</com:street1>
          <com:city>Waltham</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02451</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>08/05/2026</saleDate>
      <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
      <grossProceeds>2876145.43</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Marc N. Casper</name>
        <address>
          <com:street1>168 Third Avenue</com:street1>
          <com:city>Waltham</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02451</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>08/05/2026</saleDate>
      <amountOfSecuritiesSold>10000</amountOfSecuritiesSold>
      <grossProceeds>5752296.00</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Floral Park Associates Inc.</name>
        <address>
          <com:street1>168 Third Avenue</com:street1>
          <com:city>Waltham</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02451</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>08/06/2026</saleDate>
      <amountOfSecuritiesSold>5000</amountOfSecuritiesSold>
      <grossProceeds>2872267.69</grossProceeds>
    </securitiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Marc N. Casper</name>
        <address>
          <com:street1>168 Third Avenue</com:street1>
          <com:city>Waltham</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>02451</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>08/06/2026</saleDate>
      <amountOfSecuritiesSold>10000</amountOfSecuritiesSold>
      <grossProceeds>5744685.00</grossProceeds>
    </securitiesSoldInPast3Months>
    <remarks>Of today's sales, 4608 shares were sold from the Floral Park Associates Inc. account of which Marc N. Casper is an authorized individual and account stakeholder. In regards to sales in Securities Sold During the Past 3 Months from the Floral Park Associates Inc. account of Marc N. Casper is an authorized individual and account stakeholder. </remarks>
    <noticeSignature>
      <noticeDate>08/07/2026</noticeDate>
      <planAdoptionDates>
        <planAdoptionDate>04/27/2026</planAdoptionDate>
      </planAdoptionDates>
      <signature>/s/ Jared Cook, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Marc N. Casper</signature>
    </noticeSignature>
  </formData>
</edgarSubmission>
