    <SEC-DOCUMENT>0001133228-25-000577-index.html : 20250128
    <SEC-HEADER>0001133228-25-000577.hdr.sgml : 20250128
    <ACCEPTANCE-DATETIME>20250128084616
    ACCESSION NUMBER:		0001133228-25-000577
    CONFORMED SUBMISSION TYPE:	N-CSR
    PUBLIC DOCUMENT COUNT:		11
    CONFORMED PERIOD OF REPORT:	20241130
    FILED AS OF DATE:		20250128
    DATE AS OF CHANGE:		20250128
    EFFECTIVENESS DATE:		20250128

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			Western Asset Investment Grade Opportunity Trust Inc.
    		CENTRAL INDEX KEY:			0001462586
    		ORGANIZATION NAME:
    		IRS NUMBER:				000000000
    		STATE OF INCORPORATION:			MD
    		FISCAL YEAR END:			1130

    	FILING VALUES:
    		FORM TYPE:		N-CSR
    		SEC ACT:		1940 Act
    		SEC FILE NUMBER:	811-22294
    		FILM NUMBER:		25561102

    	BUSINESS ADDRESS:
    		STREET 1:		620 EIGHTH AVENUE
    		STREET 2:		47TH FLOOR
    		CITY:			NEW YORK
    		STATE:			NY
    		ZIP:			10018
    		BUSINESS PHONE:		888-777-0102

    	MAIL ADDRESS:
    		STREET 1:		620 EIGHTH AVENUE
    		STREET 2:		47TH FLOOR
    		CITY:			NEW YORK
    		STATE:			NY
    		ZIP:			10018

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	Western Asset Investment Grade Defined Opportunity Trust Inc.
    		DATE OF NAME CHANGE:	20090423
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>N-CSR
    <SEQUENCE>1
    <FILENAME>waigoti-efp13561_ncsr.htm
    <DESCRIPTION>WESTERN ASSET INVESTMENT GRADE OPPORTUNITY TRUST INC. (IGI) - N-CSR
    <TEXT>
    Document 1 - file: waigoti-efp13561_ncsr.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.CODE ETH
    <SEQUENCE>2
    <FILENAME>waigoti-efp13561_ex99code.htm
    <DESCRIPTION>CODE OF ETHICS
    <TEXT>
    Document 2 - file: waigoti-efp13561_ex99code.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.CERT
    <SEQUENCE>3
    <FILENAME>waigoti-efp13561_ex99cert.htm
    <DESCRIPTION>CERTIFICATIONS PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACT OF 2002
    <TEXT>
    Document 3 - file: waigoti-efp13561_ex99cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.906CERT
    <SEQUENCE>4
    <FILENAME>waigoti-efp13561_ex99906cert.htm
    <DESCRIPTION>CERTIFICATIONS PURSUANT TO SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002
    <TEXT>
    Document 4 - file: waigoti-efp13561_ex99906cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>5
    <FILENAME>imgf5b5b5be1.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 5 - file: imgf5b5b5be1.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>6
    <FILENAME>img3651a3c52.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 6 - file: img3651a3c52.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>imgfa8673903.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: imgfa8673903.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>img8c66c2da4.gif
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: img8c66c2da4.gif

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>img77cb8ff35.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: img77cb8ff35.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>img668f07506.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: img668f07506.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>imge469c0547.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: imge469c0547.jpg

    </DOCUMENT>
    </SEC-DOCUMENT>