Company: MYI
Filing Date: 2025-09-05
Form Type: 424B3
Source: 0001193125-25-196285
Chunk: 44

Company: BLACKROCK MUNIYIELD QUALITY FUND III, INC.
Filing Date: 2025-09-05
Form: 424B3
Chunk 44
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19809, and the telephone number is (800) 882-0052. Each Fund is subject to the informational requirements of the Securities Exchange Act of 1934 (the “Exchange Act”) and the 1940 Act and, in accordance therewith, file reports, proxy statements, proxy materials and other information with the SEC. Materials filed with the SEC can be downloaded from the SEC’s website at www.sec.gov. You may also request copies of these materials, upon payment at the prescribed rates of a duplicating fee, by electronic request to the SEC’s e-mailaddress (publicinfo@sec.gov). Reports, proxy statements and other information concerning the Funds may also be inspected at the offices of the NYSE, 20 Broad Street, New York, New York 10005. BlackRock updates performance information and certain other data for the Funds on a monthly basis on its website in the “Closed-EndFunds” section of www.blackrock.com as well as certain other material information as necessary from time to time. Investors and others are advised to check the website for updated performance information and the release of other material information about the Funds. References to BlackRock’s website v

are intended to allow investors public access to information regarding the Funds and do not, and are not intended to, incorporate BlackRock’s website in this Joint Proxy
Statement/Prospectus.

Please note that only one copy of shareholder documents, including annual or semi-annual reports
and proxy materials, may be delivered to two or more shareholders of the Funds who share an address, unless the Funds have received instructions to the contrary. This practice is commonly called “householding” and it is intended to
reduce expenses and eliminate duplicate mailings of shareholder documents. Mailings of your shareholder documents may be householded indefinitely unless you instruct us otherwise. To request a separate copy of any shareholder document or for
instructions as to how to request a separate copy of these documents or as to how to request a single copy if multiple copies of these documents are received, shareholders should contact the respective Fund at the address and phone number set forth
above.

The common shares of BlackRock MuniVest Fund II, Inc. are listed on the NYSE under the ticker symbol
“MVT,” the common shares of BlackRock MuniYield Michigan Quality Fund, inc. are listed on the NYSE under the ticker symbol “MIY,” and the common shares of BlackRock MuniVest Fund, Inc. are listed on the NYSE under the ticker