6-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 6-K

Report of Foreign Issuer

Pursuant to Rule 13a-16 or 15d-16

of the Securities Exchange Act of 1934

For the month of October, 2025

Commission File Number: 001-15276

Itaú Unibanco Holding S.A.

(Exact name of registrant as specified in its charter)

Itaú Unibanco Holding S.A.

(Translation of Registrant’s Name into English)

Praça Alfredo Egydio de Souza Aranha, 100 - Torre Conceição

CEP 04344-902 São Paulo, SP, Brazil

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover 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):

Yes ☐ No ☒

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):

Yes ☐ No ☒

Indicate by check mark whether by furnishing the information contained in this Form, the registrant is also thereby furnishing information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934.

Yes ☐ No ☒

If “Yes” is marked, indicate below the file number assigned to the registrant in connection with Rule 12g3-2(b):

82–___________

EXHIBIT INDEX

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: October 30, 2025.

Itaú Unibanco Holding S.A.

By: /s/ Gustavo Lopes Rodrigues

Name:     Gustavo Lopes Rodrigues

Title:    Investor Relations Officer.

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Summarized Minutes of the Meeting of the Board of Directors DATE AND TIME: On October 30, 2025, at 9:00 a.m. CHAIR: Pedro Moreira Salles and Roberto Egydio Setubal – Co-chairmen. QUORUM: The totality of the members elected, with the participation of Board members as permitted by item 6.7.1. of the Bylaws. RESOLUTIONS UNANIMOUSLY ADOPTED: 1. It is recorded the removal of the Officers (i) Thales Ferreira Silva, effective as of the present date; and (ii) João Filipe Fernandes da Costa Araújo, effective as of the date of Albano Manoel Almeida’s investiture. 2. Elected to the position of Officers of the Company: (i) ALBANO MANOEL ALMEIDA, Brazilian, married, engineer, bearer of the Identity Card (RG- SSP/SP) No. 28.198.495-5 and enrolled with the Individual Taxpayer’s Registry (CPF) under the No. 286.052.458-40; and (ii) FLAVIO RIBEIRO IGLESIAS, Brazilian, married, engineer, bearer of the Identity Card (RG- SSP/SP) No. 27.560.603-X, and enrolled with the Individual Taxpayer’s Registry (CPF) under the No. 260.111.178-05, both domiciled in the city and state of São Paulo, at Praça Alfredo Egydio de Souza Aranha, 100, Torre Olavo Setubal, Piso Itaú Unibanco, Parque Jabaquara, CEP 04344-902, for the annual term of office in course, which will be effective until the members elected at the meeting of this Board immediately after the Annual General Stockholders’ Meeting of 2026 take office. 3. It is recorded that the elected Officers: (i) submitted substantiating documents of compliance with prior conditions for eligibility pursuant to articles 146 and 147 of Law No. 6,404/76 and current regulations, particularly in Resolution No. 4,970/21 of the National Monetary Council (“CMN”) and in Attachment K of Resolution No. 80/22 of the Brazilian Securities and Exchange Commission, including clearance certificates, and all these documents were filed at the Company’s head office; and (ii) shall be vested in their positions following ratification of their election by the Central Bank of Brazil. 4. Finally, it was recorded that the other positions of the Board of Officers remained unchanged.

CLOSING: Once the work was completed, Álvaro Felipe Rizzi Rodrigues, secretary to the Board, drafted this minute, which, after being read and approved by all, was signed. São Paulo (SP), October 30, 2025. (undersigned) Pedro Moreira Salles and Roberto Egydio Setubal – Co-Chairmen; Ricardo Villela Marino – Vice-Chairman; Alfredo Egydio Setubal, Ana Lúcia de Mattos Barretto Villela, Candido Botelho Bracher, Cesar Nivaldo Gon, Fabrício Bloisi Rocha, João Moreira Salles, Marcos Marinho Lutz, Maria Helena dos Santos Fernandes de Santana, Paulo Antunes Veras and Pedro Luiz Bodin de Moraes – Board Members. GUSTAVO LOPES RODRIGUES Investor Relations Officer