<SEC-DOCUMENT>0001049502-26-000057.txt : 20260313
<SEC-HEADER>0001049502-26-000057.hdr.sgml : 20260313
<ACCEPTANCE-DATETIME>20260313101951
ACCESSION NUMBER:		0001049502-26-000057
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20260312
FILED AS OF DATE:		20260313
DATE AS OF CHANGE:		20260313

REPORTING-OWNER:	

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

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-23621
		FILM NUMBER:		26750549

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

ISSUER:		

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

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

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

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MKS INSTRUMENTS INC
		DATE OF NAME CHANGE:	19971112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>form4.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2026-03-12</periodOfReport>

    <issuer>
        <issuerCik>0001049502</issuerCik>
        <issuerName>MKS INC</issuerName>
        <issuerTradingSymbol>MKSI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001501968</rptOwnerCik>
            <rptOwnerName>Moloney Jacqueline F</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MKS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>2 TECH DRIVE</rptOwnerStreet2>
            <rptOwnerCity>ANDOVER</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>01810</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2026-03-12</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>340.107</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>213.7717</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>10393.197</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">This transaction was executed in multiple trades at prices ranging from $213.7716 to $214.015. The price reported above reflects the weighted average sale price. The reporting person hereby undertakes to provide, upon request, the full information regarding the number of shares and prices at which the transaction was effected.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ M. Kathryn Rickards, attorney-in-fact</signatureName>
        <signatureDate>2026-03-13</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
