<?xml version="1.0" encoding="UTF-8"?><edgarSubmission xmlns="http://www.sec.gov/edgar/ownership" xmlns:ns2="http://www.sec.gov/edgar/common">
    <headerData>
        <submissionType>144</submissionType>
        <filerInfo>
            <filer>
                <filerCredentials>
                    <cik>0001359098</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001093557</issuerCik>
            <issuerName>DEXCOM INC.</issuerName>
            <secFileNumber>000-51222</secFileNumber>
            <issuerAddress>
                <ns2:street1>6340 Sequence Drive</ns2:street1>
                <ns2:city>San Diego</ns2:city>
                <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                <ns2:zipCode>92121</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>(858) 200-0200</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>STEVEN PACELLI</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>38th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>412</noOfUnitsSold>
            <aggregateMarketValue>51368.16</aggregateMarketValue>
            <noOfUnitsOutstanding>387635623</noOfUnitsOutstanding>
            <approxSaleDate>04/24/2023</approxSaleDate>
            <securitiesExchangeName>NASD</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <acquiredDate>09/08/2021</acquiredDate>
            <natureOfAcquisitionTransaction>RSU</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>ISSUER</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>412</amountOfSecuritiesAcquired>
            <paymentDate>09/08/2021</paymentDate>
            <natureOfPayment>NONE</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>STEVEN PACELLI</name>
                <address>
                    <ns2:street1>6340 Sequence Drive</ns2:street1>
                    <ns2:city>San Diego</ns2:city>
                    <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                    <ns2:zipCode>92121</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <saleDate>03/23/2023</saleDate>
            <amountOfSecuritiesSold>5442</amountOfSecuritiesSold>
            <grossProceeds>633448.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>STEVEN PACELLI</name>
                <address>
                    <ns2:street1>6340 Sequence Drive</ns2:street1>
                    <ns2:city>San Diego</ns2:city>
                    <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                    <ns2:zipCode>92121</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <saleDate>03/10/2023</saleDate>
            <amountOfSecuritiesSold>11669</amountOfSecuritiesSold>
            <grossProceeds>1299914.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <securitiesSoldInPast3Months>
            <sellerDetails>
                <name>STEVEN PACELLI</name>
                <address>
                    <ns2:street1>6340 Sequence Drive</ns2:street1>
                    <ns2:city>San Diego</ns2:city>
                    <ns2:stateOrCountry>CA</ns2:stateOrCountry>
                    <ns2:zipCode>92121</ns2:zipCode>
                </address>
            </sellerDetails>
            <securitiesClassTitle>COMMON</securitiesClassTitle>
            <saleDate>02/23/2023</saleDate>
            <amountOfSecuritiesSold>412</amountOfSecuritiesSold>
            <grossProceeds>45995.00</grossProceeds>
        </securitiesSoldInPast3Months>
        <noticeSignature>
            <noticeDate>04/24/2023</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>09/15/2022</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Steven R Pacelli</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
[{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 5324}]
144
0001359098
XXXXXXXX
LIVE
0001093557
DEXCOM INC.
000-51222
6340 Sequence Drive
San Diego
CA
92121
(858) 200-0200
STEVEN PACELLI
Officer
Common
Morgan Stanley Smith Barney LLC
1 New York Plaza
38th Floor
New York
NY
10004
412
51368.16
387635623
04/24/2023
NASD
COMMON
09/08/2021
RSU
ISSUER
N
412
09/08/2021
NONE
N
STEVEN PACELLI
6340 Sequence Drive
San Diego
CA
92121
COMMON
03/23/2023
5442
633448.00
STEVEN PACELLI
6340 Sequence Drive
San Diego
CA
92121
COMMON
03/10/2023
11669
1299914.00
STEVEN PACELLI
6340 Sequence Drive
San Diego
CA
92121
COMMON
02/23/2023
412
45995.00
04/24/2023
09/15/2022
/s/ Steven R Pacelli