<SEC-DOCUMENT>0001959173-24-006756.txt : 20241001
<SEC-HEADER>0001959173-24-006756.hdr.sgml : 20241001
<ACCEPTANCE-DATETIME>20241001114409
ACCESSION NUMBER:		0001959173-24-006756
CONFORMED SUBMISSION TYPE:	144
PUBLIC DOCUMENT COUNT:		1
FILED AS OF DATE:		20241001
DATE AS OF CHANGE:		20241001

SUBJECT COMPANY:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MKS INSTRUMENTS INC
		CENTRAL INDEX KEY:			0001049502
		STANDARD INDUSTRIAL CLASSIFICATION:	INDUSTRIAL INSTRUMENTS FOR MEASUREMENT, DISPLAY, AND CONTROL [3823]
		ORGANIZATION NAME:           	08 Industrial Applications and Services
		IRS NUMBER:				042277512
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		144
		SEC ACT:		1933 Act
		SEC FILE NUMBER:	000-23621
		FILM NUMBER:		241342016

	BUSINESS ADDRESS:	
		STREET 1:		2 TECH DRIVE
		STREET 2:		SUITE 201
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		978-645-5500

	MAIL ADDRESS:	
		STREET 1:		2 TECH DRIVE
		STREET 2:		SUITE 201
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810

REPORTING-OWNER:	

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			Moloney Jacqueline F
		CENTRAL INDEX KEY:			0001501968
		ORGANIZATION NAME:           	

	FILING VALUES:
		FORM TYPE:		144

	MAIL ADDRESS:	
		STREET 1:		222 MERRIMACK STREET
		CITY:			LOWELL
		STATE:			MA
		ZIP:			01852
</SEC-HEADER>
<DOCUMENT>
<TYPE>144
<SEQUENCE>1
<FILENAME>primary_doc.xml
<TEXT>
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  <headerData>
    <submissionType>144</submissionType>
    <filerInfo>
      <filer>
        <filerCredentials>
          <cik>0001501968</cik>
          <ccc>XXXXXXXX</ccc>
        </filerCredentials>
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      <liveTestFlag>LIVE</liveTestFlag>



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  <formData>
    <issuerInfo>
      <issuerCik>0001049502</issuerCik>
      <issuerName>MKS INSTRUMENTS INC</issuerName>
      <secFileNumber>000-23621</secFileNumber>
      <issuerAddress>
        <com:street1>2 TECH DRIVE</com:street1>
        <com:street2>SUITE 201</com:street2>
        <com:city>ANDOVER</com:city>
        <com:stateOrCountry>MA</com:stateOrCountry>
        <com:zipCode>01810</com:zipCode>
      </issuerAddress>
      <issuerContactPhone>978-645-5500</issuerContactPhone>
      <nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>Moloney Jacqueline F</nameOfPersonForWhoseAccountTheSecuritiesAreToBeSold>
      <relationshipsToIssuer>
        <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>250</noOfUnitsSold>
      <aggregateMarketValue>27225.00</aggregateMarketValue>
      <noOfUnitsOutstanding>67287594</noOfUnitsOutstanding>
      <approxSaleDate>10/01/2024</approxSaleDate>
      <securitiesExchangeName>NASDAQ</securitiesExchangeName>
    </securitiesInformation>
    <securitiesToBeSold>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <acquiredDate>05/09/2022</acquiredDate>
      <natureOfAcquisitionTransaction>Restricted Stock Vesting</natureOfAcquisitionTransaction>
      <nameOfPersonfromWhomAcquired>Issuer</nameOfPersonfromWhomAcquired>
      <isGiftTransaction>N</isGiftTransaction>
      <amountOfSecuritiesAcquired>250</amountOfSecuritiesAcquired>
      <paymentDate>05/09/2022</paymentDate>
      <natureOfPayment>Compensation</natureOfPayment>
    </securitiesToBeSold>
    <nothingToReportFlagOnSecuritiesSoldInPast3Months>N</nothingToReportFlagOnSecuritiesSoldInPast3Months>
    <securitiesSoldInPast3Months>
      <sellerDetails>
        <name>Jacqueline Moloney</name>
        <address>
          <com:street1>2 Tech Drive</com:street1>
          <com:street2>Suite 201</com:street2>
          <com:city>Andover</com:city>
          <com:stateOrCountry>MA</com:stateOrCountry>
          <com:zipCode>01810</com:zipCode>
        </address>
      </sellerDetails>
      <securitiesClassTitle>Common</securitiesClassTitle>
      <saleDate>08/01/2024</saleDate>
      <amountOfSecuritiesSold>250</amountOfSecuritiesSold>
      <grossProceeds>30865.00</grossProceeds>
    </securitiesSoldInPast3Months>
    <noticeSignature>
      <noticeDate>10/01/2024</noticeDate>
      <planAdoptionDates>
        <planAdoptionDate>08/30/2023</planAdoptionDate>
      </planAdoptionDates>
      <signature>/s/ Margaret Campbell, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Jacqueline F. Moloney.</signature>
    </noticeSignature>
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</SEC-DOCUMENT>
