6-K

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, DC 20549

FORM 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of December, 2025.

Commission File Number 001-38755

Suzano S.A. (Exact name of registrant as specified in its charter)

SUZANO INC. (Translation of Registrant’s Name into English)

Av. Professor Magalhaes Neto, 1,752 10th Floor, Rooms 1010 and 1011 Salvador, Brazil 41 810-012 (Address of principal executive office)

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 ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(1): ☐

Indicate by check mark if the registrant is submitting the Form 6-K in paper as permitted by Regulation S-T Rule 101(b)(7): ☐

Enclosures:

Exhibit 99.1 – Notice to Shareholders

SIGNATURE

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 10th, 2025

Document

NOTICE TO SHAREHOLDERS

SUZANO S.A.

Publicly-held Company

Tax Id No. (CNPJ/MF) No. 16.404.287/0001-55

NIRE 29.3.0001633-1

São Paulo, December 10, 2025 – Suzano S.A. (“Company” or “Suzano”) (B3: SUZB3 | NYSE: SUZ) hereby announces to its shareholders and to the general that the Company’s Board of Directors Meeting, held on December 10, 2025, approved the distribution of interim dividends by the Company in the total amount of BRL 1,380,000,000.00 (one billion three hundred and eighty million reais), at the ratio of BRL 1.11658725 per Company share, considering the number of “ex treasury” shares on December 10, 2025, declared to the balance of retained earnings ascertained in the balance sheet of the Company dated September 30, 2025. The interim dividends declared herein will be allocated to the minimum mandatory dividend for the fiscal year ended December 31, 2025.

The payment of interim dividends will be made on February 4, 2026, in local currency, based on the shareholding position held at the end of B3 S.A. – Brasil, Bolsa, Balcão (“B3”) trading session on December 18, 2025, inclusive. The Company’s shares shall be traded “ex-dividend” as of December 19, 2025, inclusive.

The shareholders will have their credits available according to the bank domicile provided to Itaú Corretora de Valores Mobiliários S.A., institution responsible for bookkeeping the Company’s shares.

For shareholders whose registration does not contain the registration of the Individual Taxpayer Registration Number (CPF) or General Taxpayers’ Registry (CNPJ) or the indication of “Bank/Agency/Current Account”, the dividends will only be credited after the registration update and within the terms determined by Itaú Corretora de Valores Mobiliários S.A.

Regarding holders of American Depositary Receipts traded on the New York Stock Exchange - NYSE (“ADR”), the payment of interim dividends will be made in accordance with the procedures applicable by the depositary bank The Bank of New York Mellon. There will be no monetary restatement or incidence of interest between the dividend declaration date and the effective payment date.

Dividends are exempt from Income Tax, in accordance with the current legislation on this date.

The Investor Relations team is available for any further clarification, by calling +55 (11) 3503-9330 and by email [email protected].

São Paulo, December 10, 2025.

Marcos Moreno Chagas Assumpção

Executive Vice-President of Finance and Investor Relations