<?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>0001909855</cik>
                    <ccc>XXXXXXXX</ccc>
                </filerCredentials>
            </filer>
            <liveTestFlag>LIVE</liveTestFlag>



        </filerInfo>
    </headerData>
    <formData>
        <issuerInfo>
            <issuerCik>0001649904</issuerCik>
            <issuerName>RHYTHM PHARMACEUTICALS INC</issuerName>
            <secFileNumber>001-38223</secFileNumber>
            <issuerAddress>
                <ns2:street1>222 Berkeley Street, 12th Floor</ns2:street1>
                <ns2:city>BOSTON</ns2:city>
                <ns2:stateOrCountry>MA</ns2:stateOrCountry>
                <ns2:zipCode>02116</ns2:zipCode>
            </issuerAddress>
            <issuerContactPhone>8572644280</issuerContactPhone>
            <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>JOSEPH J SHULMAN</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
            <relationshipsToIssuer>
                <relationshipToIssuer>Officer</relationshipToIssuer>
            </relationshipsToIssuer>
        </issuerInfo>
        <securitiesInformation>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <brokerOrMarketmakerDetails>
                <name>Morgan Stanley Smith Barney LLC Executive Financial Services</name>
                <address>
                    <ns2:street1>1 New York Plaza</ns2:street1>
                    <ns2:street2>8th Floor</ns2:street2>
                    <ns2:city>New York</ns2:city>
                    <ns2:stateOrCountry>NY</ns2:stateOrCountry>
                    <ns2:zipCode>10004</ns2:zipCode>
                </address>
            </brokerOrMarketmakerDetails>
            <noOfUnitsSold>13281</noOfUnitsSold>
            <aggregateMarketValue>894209.73</aggregateMarketValue>
            <noOfUnitsOutstanding>61457069</noOfUnitsOutstanding>
            <approxSaleDate>11/11/2024</approxSaleDate>
            <securitiesExchangeName>NASDAQ</securitiesExchangeName>
        </securitiesInformation>
        <securitiesToBeSold>
            <securitiesClassTitle>Common</securitiesClassTitle>
            <acquiredDate>11/11/2024</acquiredDate>
            <natureOfAcquisitionTransaction>Exercise of Stock Options</natureOfAcquisitionTransaction>
            <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
            <isGiftTransaction>N</isGiftTransaction>
            <amountOfSecuritiesAcquired>13281</amountOfSecuritiesAcquired>
            <paymentDate>11/11/2024</paymentDate>
            <natureOfPayment>Cash</natureOfPayment>
        </securitiesToBeSold>
        <nothingToReportFlagOnSecuritiesSoldInPast3Months>Y</nothingToReportFlagOnSecuritiesSoldInPast3Months>
        <remarks>Sales that were executed on November 11, 2024 are being reported on this Form 144 filed on November 12, 2024 given the EDGAR system was not accepting filings November 11, 2024 in observance of the federal holiday.</remarks>
        <noticeSignature>
            <noticeDate>11/11/2024</noticeDate>
            <planAdoptionDates>
                <planAdoptionDate>08/08/2024</planAdoptionDate>
            </planAdoptionDates>
            <signature>/s/ Joseph Shulman</signature>
        </noticeSignature>
    </formData>
</edgarSubmission>
[{"type": "144", "sequence": "1", "filename": "primary_doc.xml", "secsgml_size_bytes": 3562}]
144
0001909855
XXXXXXXX
LIVE
0001649904
RHYTHM PHARMACEUTICALS INC
001-38223
222 Berkeley Street, 12th Floor
BOSTON
MA
02116
8572644280
JOSEPH J SHULMAN
Officer
Common
Morgan Stanley Smith Barney LLC Executive Financial Services
1 New York Plaza
8th Floor
New York
NY
10004
13281
894209.73
61457069
11/11/2024
NASDAQ
Common
11/11/2024
Exercise of Stock Options
Issuer
N
13281
11/11/2024
Cash
Y
Sales that were executed on November 11, 2024 are being reported on this Form 144 filed on November 12, 2024 given the EDGAR system was not accepting filings November 11, 2024 in observance of the federal holiday.
11/11/2024
08/08/2024
/s/ Joseph Shulman