Company: MYI
Filing Date: 2025-09-08
Form Type: DEF 14A
Source: 0001193125-25-198172
Chunk: 0

Company: BLACKROCK MUNIYIELD QUALITY FUND III, INC.
Filing Date: 2025-09-08
Form: DEF 14A
Chunk 0
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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 SCHEDULE 14A INFORMATION Proxy Statement Pursuant to Section 14(a) of the Securities Exchange Act of 1934 Filed by the Registrant ☒ Filed by a Party other than the Registrant ☐ Check the appropriate box: ☐ Preliminary Proxy Statement ☐ Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)) ☒ Definitive Proxy Statement ☐ Definitive Additional Materials ☐ Soliciting Material Pursuant to § 240.14a-12 BLACKROCK MUNIVEST FUND II, INC. BLACKROCK MUNIYIELD MICHIGAN QUALITY FUND, INC. BLACKROCK MUNIVEST FUND, INC. BLACKROCK MUNIYIELD QUALITY FUND III, INC. (Name of Registrant as Specified In Its Charter) (Name of Person(s) Filing Proxy Statement, if Other than the Registrant)

| Payment of Filing Fee (Check the appropriate box):                                                     |
| ☒ No fee required.                                                                                     |
| ☐ Fee paid previously with preliminary materials.                                                      |
| ☐ Fee computed on table in exhibit required by Item 25(b) per Exchange Act Rules 14a-6(i)(1) and 0-11. |

BLACKROCK MUNIVEST FUND II, INC.

BLACKROCK MUNIYIELD MICHIGAN QUALITY FUND, INC.

BLACKROCK MUNIVEST FUND, INC.

BLACKROCK MUNIYIELD QUALITY FUND III, INC.

100 Bellevue Parkway

Wilmington, Delaware 19809

(800) 882-0052

September 8, 2025

Dear
Preferred Shareholder:

You are cordially invited to attend a joint special shareholder meeting (the “Special Meeting”) of
BlackRock MuniVest Fund II, Inc. (“MVT”), BlackRock MuniYield Michigan Quality Fund, Inc. (“MIY”), BlackRock MuniVest Fund, Inc. (“MVF”) and BlackRock MuniYield Quality Fund III, Inc. (“MYI” or the
“Acquiring Fund” and collectively with MVT, MIY and MVF, the “Funds,” and each, a “Fund”), to be held on October 15