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 13, 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

UPDATE: INCIDENT AT SAMARCO

This update provides further information on the incident at the Samarco Mineração S.A (Samarco) iron ore operation in Minas Gerais, Brazil on Thursday, 5 November 2015. Each of BHP Billiton and Vale holds a 50 percent interest in Samarco.

Samarco has advised that, at this stage, there are nine fatalities. Samarco has also advised that four people previously unaccounted for have been found and 19 people remain unaccounted for.

We offer our deepest sympathies to the families and friends of those who have died as a result of this tragic incident.

BHP Billiton’s immediate priority is the welfare of the Samarco workforce and the community. The local authorities have advised that through the emergency response, 637 people have been evacuated and temporary accommodation has been provided. Samarco and authorities are providing water and food aid to affected communities.

BHP Billiton and Vale have pledged to support Samarco in establishing an emergency fund for community support and rebuilding works. It is our intention to work with the authorities to ensure that this fund is functioning as soon as practicable.

Minimising the environmental impact of this incident is also a priority and an Environmental Recovery Plan is to be developed by Samarco with the support of an external expert.

At this stage, the tailings extend 440 kilometres downstream and 11 communities have been affected. Samarco has put in place a water monitoring program for the ongoing analysis of the water quality of the Gualaxo do Norte, Carmo and Doce Rivers. Samarco is working with relevant authorities to manage river water quality and ensure availability of potable water.

Samarco employees have been put on paid leave and options are being considered by Samarco for managing the workforce longer term.

Samarco is continuing to monitor the impacted tailings facilities, including the Germano dam. In conjunction with independent experts, Samarco is developing a plan to reinforce the dam structures and stabilise the area.

Samarco operations were immediately stopped following the incident and Samarco’s operating licence has been suspended. The Samarco operations will remain suspended as authorities commence investigations and rectification work plans are developed.

Samarco and representatives of BHP Billiton and Vale are meeting with lead insurers in Brazil this week.

Further updates will be provided when information becomes available.

Further information on BHP Billiton can be found at: www.bhpbilliton.com.

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.