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

November 3, 2025

Commission File Number 1-10167

WESTPAC BANKING CORPORATION

(Translation of registrant’s name into English)

275 KENT STREET, SYDNEY, NEW SOUTH WALES 2000, AUSTRALIA

(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 x         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): ¨

Incorporation by Reference

The information contained in this Report on Form 6-K, excluding the information set forth in Exhibit No. 1, shall be incorporated by reference in the prospectuses relating to the Registrant’s securities contained in the Registrant’s Registration Statements on Form F-3 (File Nos. 333-283007 and 333-283008), as such prospectuses may be amended or supplemented from time to time.

Westpac sells RAMS mortgage portfolio

Westpac today announced it has entered into an agreement to sell its $21.4bn RAMS mortgage portfolio to a consortium which includes Pepper Money Limited, KKR and PIMCO. The sale represents the whole of the RAMS branded mortgage portfolio.

The sale is at a slight premium to the gross loan value of the portfolio to be transferred at completion. After transaction costs and other adjustments, a loss on sale is expected.

Following completion, Westpac’s common equity Tier 1 capital ratio is estimated to increase by c.20 bps.

Completion of the transaction is subject to various conditions and regulatory approvals and is expected to occur in 2H26.

Index to Exhibits

Disclosure regarding forward-looking statements

The information contained in this Report on Form 6-K contains statements that constitute “forward-looking statements” within the meaning of section 21E of the U.S. Securities Exchange Act of 1934.

Forward-looking statements are statements that are not historical facts. Forward-looking statements appear in a number of places in this Report and include statements regarding Westpac’s current intent, belief or expectations with respect to its business and operations, macro and micro economic and market conditions, results of operations and financial condition and performance, capital adequacy and liquidity and risk management, including, without limitation, future loan loss provisions and financial support to certain borrowers, forecasted economic indicators and performance metric outcomes, indicative drivers, climate- and other sustainability-related statements, commitments, targets, projections and metrics, and other estimated and proxy data.

Words such as ‘will’, ‘may’, ‘expect’, ‘intend’, ‘seek’, ‘would’, ‘should’, ‘could’, ‘continue’, ‘plan’, ‘estimate’, ‘anticipate’, ‘believe’, ‘probability’, ‘indicative’, ‘risk’, ‘aim’, ‘outlook’, ‘forecast’, ‘assumption’, ‘projection’, ‘target’, ‘goal’, ‘guidance’, ‘objective’, ‘ambition’ or other similar words, are used to identify forward-looking statements. These statements reflect Westpac’s current views on future events and are subject to change, certain known and unknown risks, uncertainties and assumptions and other factors which are, in many instances, beyond Westpac’s control (and the control of Westpac’s officers, employees, agents and advisors), and have been made based on management’s and/or the Board’s current expectations or beliefs concerning future developments and their potential effect upon Westpac.

Forward-looking statements may also be made, verbally or in writing, by members of Westpac’s management or Board in connection with this Report. Such statements are subject to the same limitations, uncertainties, assumptions and disclaimers set out in this Report.

There can be no assurance that future developments or performance will align with Westpac’s expectations or that the effect of future developments on Westpac will be those anticipated. Actual results could differ materially from those Westpac expects or which are expressed or implied in forward-looking statements, depending on various factors including, but not limited to, those described in the risk factors in Westpac’s 2025 Risk Factors on Form 6-K filed with the U.S. Securities and Exchange Commission. When relying on forward-looking statements to make decisions with respect to us, investors and others relying on information in this Report should carefully consider such factors and other uncertainties and events.

Except as required by law, Westpac assumes no obligation to revise or update any forward-looking statements in this Report, whether from new information, future events, conditions or otherwise, after the date of this Report.