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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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 TWSM7vrzLADbmYQaionwg5sDW3P6oaM5D3tdezXMm7z1T+B+twIDAQAB
MIC-Info: RSA-MD5,RSA,
 SW5L7mFudkSrZj53Z2SrXqEXO0cC/aexBdIAjcJDGKt9WXgamJvnPClcoyfAoewB
 9CpaQ6DHWSqDl/oW9766Ww==

<SEC-DOCUMENT>0001250608-03-000015.txt : 20031030
<SEC-HEADER>0001250608-03-000015.hdr.sgml : 20031030
<ACCEPTANCE-DATETIME>20031030141314
ACCESSION NUMBER:		0001250608-03-000015
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20031028
FILED AS OF DATE:		20031030

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			WELDON DENNIS M
		CENTRAL INDEX KEY:			0001239186

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-13442
		FILM NUMBER:		03966201

	MAIL ADDRESS:	
		STREET 1:		C/OMENTOR GRAPHICS CORP
		STREET 2:		8005 SW BOECKMAN ROAD
		CITY:			WILSONVILLE
		STATE:			OR
		ZIP:			97070-7777

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MENTOR GRAPHICS CORP
		CENTRAL INDEX KEY:			0000701811
		STANDARD INDUSTRIAL CLASSIFICATION:	SERVICES-COMPUTER INTEGRATED SYSTEMS DESIGN [7373]
		IRS NUMBER:				930786033
		STATE OF INCORPORATION:			OR
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		8005 SW BOECKMAN RD
		CITY:			WILSONVILLE
		STATE:			OR
		ZIP:			97070-7777
		BUSINESS PHONE:		5036857000
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-10-28</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000701811</issuerCik>
        <issuerName>MENTOR GRAPHICS CORP</issuerName>
        <issuerTradingSymbol>MENT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001239186</rptOwnerCik>
            <rptOwnerName>WELDON DENNIS M</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/OMENTOR GRAPHICS CORP</rptOwnerStreet1>
            <rptOwnerStreet2>8005 SW BOECKMAN ROAD</rptOwnerStreet2>
            <rptOwnerCity>WILSONVILLE</rptOwnerCity>
            <rptOwnerState>OR</rptOwnerState>
            <rptOwnerZipCode>97070-7777</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Treasurer</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>

        <derivativeTransaction>
            <securityTitle>
                <value>Employee Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.25</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-10-28</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>20000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.25</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2003-10-28</value>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-10-28</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>20000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>

    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares become exercisable for 25% of the total shares on 10/28/2004.  The remaining 75% vest monthly for 1/48th of the total shares, for the next 3 years.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Dean Freed, Attorney-in-fact for Dennis M. Weldon</signatureName>
        <signatureDate>2003-10-30</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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