# EDGAR Filing Document

**Accession Number:** 0001073404
**File Stem:** 0001104659-25-123124
**Filing Date:** 2025-12
**Character Count:** 3331
**Document Hash:** e92c1b503232548570bdc2790dc95af3
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001104659-25-123124.hdr.sgml**: 20251219

**ACCESSION NUMBER**: 0001104659-25-123124

**CONFORMED SUBMISSION TYPE**: 6-K

**PUBLIC DOCUMENT COUNT**: 3

**CONFORMED PERIOD OF REPORT**: 20251219

**FILED AS OF DATE**: 20251219

**DATE AS OF CHANGE**: 20251219

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** GERDAU S.A.
- **CENTRAL INDEX KEY:** 0001073404
- **STANDARD INDUSTRIAL CLASSIFICATION:** STEEL WORKS, BLAST FURNACES & ROLLING & FINISHING MILLS [3310]
- **ORGANIZATION NAME:** 04 Manufacturing
- **EIN:** 000000000
- **STATE OF INCORPORATION:** D5
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 6-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-14878
- **FILM NUMBER:** 251587619

**BUSINESS ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** AV DOUTORA RUTH CARDOSO, 8,501
- **STREET 2:** 8TH FLOOR
- **CITY:** SAO PAULO, SP
- **PROVINCE COUNTRY:** D5
- **ZIP:** 05425-070
- **BUSINESS PHONE:** 011-55-51-3323-2703

**MAIL ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** AV DOUTORA RUTH CARDOSO, 8,501
- **STREET 2:** 8TH FLOOR
- **CITY:** SAO PAULO, SP
- **PROVINCE COUNTRY:** D5
- **ZIP:** 05425-070

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** GERDAU SA
- **DATE OF NAME CHANGE:** 19981112

**U.S. SECURITIES AND EXCHANGE COMMISSION**

**Washington, D.C. 20549**

**FORM 6-K**

**REPORT OF FOREIGN PRIVATE ISSUER**

**PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE**

**SECURITIES EXCHANGE ACT OF 1934**

Dated December 19, 2025

Commission File Number 1-14878

**GERDAU S.A.**

(Translation of Registrant's Name into English)

Av. Dra. Ruth Cardoso, 8,501 – 8° andar

São Paulo, São Paulo - Brazil CEP 05425-070

(Address of principal executive offices)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F ⌧ Form 40-F ◻

<u>Exhibit Index</u>

<u>Exhibit</u> <u>Description of Exhibit</u> <br>[99.1](tm2534001d1_ex99-1.htm) [Material Fact – Buyback program conclusion](tm2534001d1_ex99-1.htm)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this Report to be signed on its behalf by the undersigned, thereunto duly authorized.

Date: December 19, 2025

---

| | |
|:---|:---|
| GERDAU S.A. | GERDAU S.A. |
| By: | /s/ Rafael Dorneles Japur |
| Name: | Rafael Dorneles Japur |
| Title: | Vice-President and Investor Relations Officer |

---

## Exhibit 99.1

**Exhibit 99.1**

![](tm2534001d1_ex99-1img001.jpg)

**GERDAU S.A.** 

Tax ID (CNPJ) 33.611.500/0001-19

Registry (NIRE): 35300520696

**MATERIAL FACT**

**GERDAU S.A.** (B3: GGBR / NYSE: GGB) ("Company") informs its shareholders and the market in general that the share buyback program issued by the Company ("2025 Buyback Program"), disclosed by Material Fact on January 20, 2025, was concluded on this date.

During the period of the buyback, 1,500,000 common shares (GGBR3) were acquired at an average price of R$15.65 per share and 63,000,000 preferred shares (GGBR4 and/or ADRs backed by preferred shares (GGB)) at an average price of R$16.27, corresponding to 100% of the 2025 Buyback Program.

São Paulo, December 19, 2025.

**Rafael Dorneles Japur** 

Executive Vice-President and Investor Relations Officer