UNITED STATES

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

November 6, 2015

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

Indicate by check mark whether the registrant by furnishing the information contained in this Form is also thereby furnishing the information to the Commission pursuant to Rule 12g3-2(b) under the Securities Exchange Act of 1934:    ¨  Yes    x  No

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

NEWS RELEASE

INCIDENT AT SAMARCO

BHP Billiton understands that a serious incident has occurred at Samarco Mineração S.A’s iron ore operation in Minas Gerais, Brazil. BHP Billiton holds a 50% interest in that entity. Samarco Mineração S.A is the operator.

BHP Billiton is concerned for the safety of employees and the local community.

We are in the process of obtaining more details from Samarco Mineração S.A.

We will provide updated information on the situation as soon as we are in a position to do so.

Members of the BHP Billiton Group which is headquartered in Australia

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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.