Exhibit 8.1

TELEPHONE: 1-212-558-4000 FACSIMILE: 1-212-558-3588 WWW.SULLCROM.COM

125 Broad Street New York, New York 10004-2498     LOS ANGELES • PALO ALTO • WASHINGTON, D.C. BRUSSELS • FRANKFURT • LONDON • PARIS BEIJING • HONG KONG • TOKYO MELBOURNE • SYDNEY

September 14, 2026

First Hawaiian, Inc.

999 Bishop St., 29th Floor

Honolulu, Hawaii 96813

Ladies and Gentlemen:

Reference is made to the Registration Statement on Form S-4, including the joint proxy statement/prospectus, forming a part thereof (as amended or supplemented through the date hereof, the “Registration Statement”) of First Hawaiian, Inc., a Delaware corporation (“First Hawaiian”), relating to the proposed mergers by and among First Hawaiian, TriCo Bancshares, a California corporation (“TriCo”) and Horizon Merger Sub, Inc., a California corporation and a direct, wholly owned subsidiary of First Hawaiian.

We have participated in the preparation of the discussion set forth in the section entitled “MATERIAL U.S. FEDERAL INCOME TAX CONSEQUENCES OF THE MERGERS” in the Registration Statement. In our opinion, such discussion, insofar as it summarizes United States federal income tax law, and subject to the qualifications, exceptions, assumptions and limitations described therein, is accurate in all material respects.

We hereby consent to the filing of this opinion with the Securities and Exchange Commission as an exhibit to the Registration Statement and to the references therein to us. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act of 1933, as amended.