Exhibit 5.1

Linklaters LLP One Silk Street London EC2Y 8HQ Telephone (+44) 20 7456 2000 Facsimile (+44) 20 7456 2222 DX Box Number 10 CDE

The Directors

Rio Tinto Finance (USA) plc

St. James’s Square

London SW1Y 4AD

England

The Directors

Rio Tinto Finance (USA) Limited

120 Collins Street

Melbourne

Victoria 3000

Australia

The Directors

Rio Tinto plc

St. James’s Square London SW1Y 4AD

England

The Directors

Rio Tinto Limited

120 Collins Street

Melbourne

Victoria 3000

Australia

May 8, 2017

Dear Sirs

Rio Tinto Finance (USA) Limited (ACN 062 129 551) and Rio Tinto Finance (USA) plc Registration Statement on Form F-3 in respect of debt securities

1 We have acted as English legal advisers to Rio Tinto Finance (USA) plc, a company incorporated under the laws of England, Rio Tinto Finance (USA) Limited, a company incorporated under the laws of the State of Victoria, Commonwealth of Australia (together with Rio Tinto Finance (USA) plc, the “Issuers”), Rio Tinto plc, a company incorporated under the laws of England (“Rio Tinto plc”) and Rio Tinto Limited, a company incorporated under the laws of the State of Victoria, Commonwealth of Australia (“Rio Tinto Limited” and, together with Rio Tinto plc, the “Guarantors”), in connection with the automatic shelf registration statement on Form F-3 filed with

This communication is confidential and may be privileged or otherwise protected by work product immunity.

Linklaters LLP is a limited liability partnership registered in England and Wales with registered number OC326345. It is a law firm authorised and regulated by the Law Society of England and Wales. The term partner in relation to Linklaters LLP is used to refer to a member of Linklaters LLP or an employee or consultant of Linklaters LLP or any of its affiliated firms or entities with equivalent standing and qualifications. A list of the names of the members of Linklaters LLP together with a list of those non-members who are designated as partners and their professional qualifications is open to inspection at its registered office, One Silk Street, London EC2Y 8HQ or on www.linklaters.com and such persons are either solicitors, registered foreign lawyers or European lawyers.

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the United States Securities and Exchange Commission on May 8, 2017 (the “Registration Statement”) relating to the registration under the United States Securities Act of 1933 (the “Act”) of (i) an indeterminate amount of the Issuers’ debt securities (the “Debt Securities”), which, if issued, will be unconditionally guaranteed as to payment of principal, premium, if any, and interest (the “Guarantees”) by each of the Guarantors and (ii) the Guarantees. The Debt Securities may be issued from time to time pursuant to the Indenture (as defined in the Schedule to this opinion).

2 This opinion is limited to English law as applied by the English courts in effect on the date of this opinion. It is given on the basis that it will be governed by and construed in accordance with English law. In particular, we express no opinion on matters of federal law of the United States, the laws of any State of the United States, Australian laws or the laws of any other jurisdiction.

3 For the purpose of this opinion we have examined the documents listed and, where appropriate, defined in the Schedule to this opinion.

4 We have assumed that:

4.1 (except in the case of Rio Tinto plc and Rio Tinto Finance (USA) plc) all relevant documents are within the capacity and powers of, and have been validly authorised by, each of the respective parties thereto;

4.2 the Minutes (as defined below) and other corporate documents are a true and complete record of the proceedings and resolutions described therein and there has been no modification of the Articles, and there was no modification of the Original Articles in force on the date of the Original Indenture, in each case examined by us and referred to in the Schedule to this opinion;

4.3 the Meeting of the Chairman’s Committee of the Board of Directors of Rio Tinto plc held on March 16, 2012 (in respect of which extracts of the minutes (the “RTPLC Minutes”) have been supplied to us) and the Meetings of the Board of Directors of Rio Tinto plc held on April 21, 2004, February 9, 2010, and May 2, 2017 (in respect of which certified extracts of the minutes (together with the RTPLC Minutes, the “Guarantor Minutes”) have been supplied to us) were in each case duly convened and constituted, a quorum was present and acting throughout and the resolutions referred to in the Guarantor Minutes were duly and validly passed and have not been amended, modified or rescinded;

4.4 the Meetings of the Board of Directors of Rio Tinto Finance (USA) plc held on March 16, 2012 and May 3, 2017 (in respect of which extracts of the minutes (the “Issuer Minutes” and, together with the Guarantor Minutes, the “Minutes”) have been supplied to us) were in each case duly convened and constituted, a quorum was present and acting throughout and the resolutions referred to in the Issuer Minutes were duly and validly passed and have not been amended, modified or rescinded;

4.5 all documents furnished to us as copies are genuine, authentic and complete and conform to the original documents of which they are copies and the genuineness of all signatures thereon or on the original thereof and the relevant documents have been executed in the forms reviewed by us;

4.6 there will be no provision in any supplement to the Registration Statement or any other document which would affect the content of this opinion;

4.7 the Debt Securities will not be redeemable at a premium that exceeds that generally payable in respect of debt securities with a similar nominal value that are listed on the London Stock Exchange plc; and

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4.8 the interest payable on the Debt Securities will not exceed a reasonable commercial return on the principal amount of the Debt Securities.

5 Based on the documents referred to, and assumptions made, in paragraphs 3 and 4 above, and subject to the qualifications in paragraphs 6 to 8 below and to any matters not disclosed to us, we are of the following opinion:

5.1 Rio Tinto plc is a company incorporated in England under the Companies Acts 1948 to 1980 and Rio Tinto Finance (USA) plc is a company incorporated in England under the Companies Act 2006.

5.2 Each of Rio Tinto Finance (USA) plc and Rio Tinto plc has corporate power to enter into, and perform its obligations under, the Indenture and has taken all necessary corporate action to authorise the execution, delivery and performance of the Indenture.

6 This opinion is subject to the following: save in relation to paragraph 5.3 above, it should be understood that we have not been responsible for investigating or verifying the accuracy of the facts, including statements of foreign law, or the reasonableness of any statements of opinion, contained in the Registration Statement, or that no material facts have been omitted from it.

7 This opinion is given on the basis of English law in force, and as it affects the obligations under the Indenture, the Debt Securities and/or the relevant Guarantee, as at the date of this opinion. This opinion is given on the basis that there will be no amendment to or termination or replacement of the documents, authorisations and consents referred to in the Schedule to this opinion. This opinion is also given on the basis that we undertake no responsibility to notify any addressee of this opinion of any change in English law after the date of this opinion.

8 We express no opinion as to the compliance or otherwise with any financial limitations on borrowings contained in the Articles.

9 We hereby consent to the filing of this opinion as an exhibit to the Registration Statement and to the reference to us made under the heading “Legal Matters” in the Registration Statement. In giving this consent we do not admit that we are within the category of persons whose consent is required within Section 7 of the Act or the rules and regulations of the Securities and Exchange Commission thereunder.

Yours faithfully

/s/ Linklaters LLP

Linklaters LLP

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SCHEDULE

1 Certified copies of (a) the Memorandum and Articles of Association of Rio Tinto Finance (USA) plc and (b) the Memorandum and Articles of Association of Rio Tinto plc, in each case in force as at the date of this opinion (together, the “Articles”).

2 Certified copies of (a) the Memorandum and Articles of Association of Rio Tinto Finance (USA) plc and (b) the Memorandum and Articles of Association of Rio Tinto plc, in each case in force as at the date of execution of the Original Indenture (together, the “Original Articles”).

3 Extract from the Minutes of Meetings of the Board of Directors of Rio Tinto Finance (USA) plc held on March 16, 2012 and May 3, 2017.

4 A copy of the executed power of attorney of Rio Tinto Finance (USA) plc dated March 15, 2012.

5 Extracts from the Minutes of a Meeting of the Chairman’s Committee of the Board of Directors of Rio Tinto plc held on March 15, 2012.

6 Certified extracts from the Minutes of a Meeting of the Board of Directors of Rio Tinto plc held on April 21, 2004, February 9, 2010 and May 2, 2017.

7 A copy of the executed certificate delegating authority of the Chief Financial Officer of Rio Tinto plc dated May 5, 2017.

8 The Registration Statement.

9 Amended and Restated Indenture dated March 16, 2012 (the “Original Indenture”) and the First Supplemental Indenture dated May 8, 2017 (together with the Original Indenture, the “Indenture”) among the Issuers, the Guarantors and The Bank of New York Mellon acting as trustee.

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