Company: MGRE
Filing Date: 2025-04-11
Form Type: DEFA14A
Source: 0001004434-25-000024
Chunk: 0

Company: AFFILIATED MANAGERS GROUP, INC.
Filing Date: 2025-04-11
Form: DEFA14A
Chunk 0
---
### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

#### SCHEDULE 14A
<div align='center'>Proxy Statement Pursuant to Section 14(a) of the Securities</div>

#### Exchange Act of 1934 (Amendment No. )
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

#### AFFILIATED MANAGERS GROUP, INC.
<div align='center'>(Name of Registrant as Specified In Its Charter)</div>

<div align='center'>(Name of Person(s) Filing Proxy Statement, if other than the Registrant)</div>

Payment of Filing Fee (Check all boxes that apply):

☒ 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

Your Vote Counts! Affiliated Managers Group, Inc. 2025 Annual Meeting Vote by May 21, 2025 11:59 PM EDT AMG AFFILIATED MANAGERS GROUP, INC. 777 SOUTH FLAGLER DRIVE WEST PALM BEACH, FL 33401

You invested in AFFILIATED MANAGERS GROUP, INC. and it’s time to vote! You have the right to vote on proposals being presented at the Annual Meeting. This is an important notice regarding the availability of proxy materials for the stockholder meeting to be held on May 22, 2025. Get informed before you vote View the Notice and Proxy Statement and Form 10-K online OR you can receive a free paper or email copy of the material(s) by requesting prior to May 8, 2025. If you would like to request a copy of the material(s) for this and/or future stockholder meetings, you may (1) visit www.ProxyVote.com, (2) call 1-800-579-1639 or (3) send an email to sendmaterial@proxyvote.com. If sending an email, please include your control number (indicated below)