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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,
 J5QEjeCyi/CKdSTHXnC+ruxF/1HIQvls5xHTXEQfVfGUBRGQJC0gr4vLN5lfpczQ
 KSNHz2QBf1315AB5qttbHw==

<SEC-DOCUMENT>0001250608-04-000010.txt : 20040520
<SEC-HEADER>0001250608-04-000010.hdr.sgml : 20040520
<ACCEPTANCE-DATETIME>20040520155415
ACCESSION NUMBER:		0001250608-04-000010
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20040419
FILED AS OF DATE:		20040520

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

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RICHARDSON FONTAINE K
		CENTRAL INDEX KEY:			0001197823

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-13442
		FILM NUMBER:		04821448

	BUSINESS ADDRESS:	
		STREET 1:		120 FLANDERS RD
		STREET 2:		PO BOX 5013
		CITY:			WESTBORO
		STATE:			MA
		ZIP:			01581
		BUSINESS PHONE:		5088981000
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2004-04-19</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001197823</rptOwnerCik>
            <rptOwnerName>RICHARDSON FONTAINE K</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O MENTOR GRAPHICS CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>8005 SW BOECKMAN RD</rptOwnerStreet2>
            <rptOwnerCity>WILSONVILLE</rptOwnerCity>
            <rptOwnerState>OR</rptOwnerState>
            <rptOwnerZipCode>97070-7777</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Director option, right to buy</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>16.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-04-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>12000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>16.5</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-04-19</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>12000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>12000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Shares become exercisable for 20% of the total shares granted, on the first 5 anniversaries of the grant date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Dean Freed, Attorney in fact for Fontaine K. Richardson</signatureName>
        <signatureDate>2004-04-20</signatureDate>
    </ownerSignature>
</ownershipDocument>

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