    <SEC-DOCUMENT>0001193125-21-290639-index.html : 20211004
    <SEC-HEADER>0001193125-21-290639.hdr.sgml : 20211004
    <ACCEPTANCE-DATETIME>20211004115706
    ACCESSION NUMBER:		0001193125-21-290639
    CONFORMED SUBMISSION TYPE:	N-CSR
    PUBLIC DOCUMENT COUNT:		21
    CONFORMED PERIOD OF REPORT:	20210731
    FILED AS OF DATE:		20211004
    DATE AS OF CHANGE:		20211004
    EFFECTIVENESS DATE:		20211004

    FILER:

    	COMPANY DATA:
    		COMPANY CONFORMED NAME:			BLACKROCK MUNIYIELD QUALITY FUND III, INC.
    		CENTRAL INDEX KEY:			0000883412
    		IRS NUMBER:				223165131
    		FISCAL YEAR END:			1031

    	FILING VALUES:
    		FORM TYPE:		N-CSR
    		SEC ACT:		1940 Act
    		SEC FILE NUMBER:	811-06540
    		FILM NUMBER:		211301552

    	BUSINESS ADDRESS:
    		STREET 1:		100 BELLEVUE PARKWAY
    		CITY:			WILMINGTON
    		STATE:			DE
    		ZIP:			19809
    		BUSINESS PHONE:		800-441-7762

    	MAIL ADDRESS:
    		STREET 1:		100 BELLEVUE PARKWAY
    		CITY:			WILMINGTON
    		STATE:			DE
    		ZIP:			19809

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	BLACKROCK MUNIYIELD QUALITY FUND III, INC
    		DATE OF NAME CHANGE:	20101109

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	BLACKROCK MUNIYIELD INSURED FUND, INC
    		DATE OF NAME CHANGE:	20070612

    	FORMER COMPANY:
    		FORMER CONFORMED NAME:	MUNIYIELD INSURED FUND INC
    		DATE OF NAME CHANGE:	19920717
    </SEC-HEADER>
    <DOCUMENT>
    <TYPE>N-CSR
    <SEQUENCE>1
    <FILENAME>d211112dncsr.htm
    <DESCRIPTION>BLACKROCK MUNIYIELD QUALITY FUND III, INC.
    <TEXT>
    Document 1 - file: d211112dncsr.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.CERT
    <SEQUENCE>2
    <FILENAME>d211112dex99cert.htm
    <DESCRIPTION>CERTIFICATION PURSUANT TO SECTION 302
    <TEXT>
    Document 2 - file: d211112dex99cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.906CERT
    <SEQUENCE>3
    <FILENAME>d211112dex99906cert.htm
    <DESCRIPTION>CERTIFICATION PURSUANT TO SECTION 906
    <TEXT>
    Document 3 - file: d211112dex99906cert.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.PROXYPOL
    <SEQUENCE>4
    <FILENAME>d211112dex99proxypol.htm
    <DESCRIPTION>PROXY VOTING POLICY
    <TEXT>
    Document 4 - file: d211112dex99proxypol.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.GLOBAL.CORP.GO
    <SEQUENCE>5
    <FILENAME>d211112dex99globalcorpgo.htm
    <DESCRIPTION>GLOBAL CORPORATE GOVERNANCE & ENGAGEMENT PRINCIPLES
    <TEXT>
    Document 5 - file: d211112dex99globalcorpgo.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>EX-99.US.CORP.GOV
    <SEQUENCE>6
    <FILENAME>d211112dex99uscorpgov.htm
    <DESCRIPTION>CORPORATE GOVERNANCE AND PROXY VOTING GUIDELINES FOR U.S. SECURITIES
    <TEXT>
    Document 6 - file: d211112dex99uscorpgov.htm

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>7
    <FILENAME>g204664b1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 7 - file: g204664b1.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>8
    <FILENAME>g204664dsp15a.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 8 - file: g204664dsp15a.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>9
    <FILENAME>g204664dsp15b.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 9 - file: g204664dsp15b.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>10
    <FILENAME>g204664g1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 10 - file: g204664g1.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>11
    <FILENAME>g204664k1.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 11 - file: g204664k1.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>12
    <FILENAME>g2123826.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 12 - file: g2123826.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>13
    <FILENAME>g2123829.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 13 - file: g2123829.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>14
    <FILENAME>g212382d92.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 14 - file: g212382d92.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>15
    <FILENAME>g212382ds92.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 15 - file: g212382ds92.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>16
    <FILENAME>g212382g42l24.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 16 - file: g212382g42l24.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>17
    <FILENAME>g212382nnu.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 17 - file: g212382nnu.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>18
    <FILENAME>g212382photo_01mips.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 18 - file: g212382photo_01mips.jpg

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    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>19
    <FILENAME>g212382sig_01mips.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 19 - file: g212382sig_01mips.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>20
    <FILENAME>g212382snap15.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 20 - file: g212382snap15.jpg

    </DOCUMENT>
    <DOCUMENT>
    <TYPE>GRAPHIC
    <SEQUENCE>21
    <FILENAME>g212382snap2.jpg
    <DESCRIPTION>GRAPHIC
    <TEXT>
    Document 21 - file: g212382snap2.jpg

    </DOCUMENT>
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