Company: IPGP
Filing Date: 2025-05-02
Form Type: DEFA14A
Source: 0001111928-25-000064
Chunk: 0

Company: IPG PHOTONICS CORP
Filing Date: 2025-05-02
Form: DEFA14A
Chunk 0
---
### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549
<div align='center'>(Rule 14a-101)</div>

#### SCHEDULE 14A

#### Proxy Statement Pursuant to Section 14(a) of the
<div align='center'>Securities Exchange Act of 1934 (Amendment No.__ )</div>

| þ |     | 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                                                      |
| þ                          |     | Definitive Additional Materials                                                 |
| ¨                          |     | Soliciting Material Pursuant to Section 240.14a-12                              |

#### IPG Photonics Corporation
<div align='center'>(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than the Registrant)</div>

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

#### Explanatory Note
This proxy supplement, dated May 2, 2025 (this “Supplement”), supplements the definitive proxy statement of IPG Photonics Corporation (the “Company”) dated April 7, 2025 (the “Proxy Statement”), for the Company’s 2025 Annual Meeting of Stockholders to be held on May 20, 2025, at 10:00 am Eastern Time (the “Annual Meeting”).

THIS SUPPLEMENT SHOULD BE READ IN CONJUNCTION WITH THE PROXY STATEMENT. EXCEPT AS SPECIFICALLY SUPPLEMENTED BY THE INFORMATION CONTAINED HEREIN, THIS SUPPLEMENT DOES NOT MODIFY ANY OTHER INFORMATION SET FORTH IN THE PROXY STATEMENT.

Composition Change to Nominating and Corporate Governance Committee

Today we are announcing that Natalia Pavlo