On 22 May 2025, the United Kingdom signed a treaty transferring sovereignty of the Chagos Islands to Mauritius, concluding a protracted territorial dispute.

The agreement ensures the UK and the United States retain operational control over the Diego Garcia military base through a 99-year lease, with an annual payment of approximately £101 million to Mauritius.

The treaty follows a 2019 International Court of Justice advisory opinion deeming the UK's continued administration of the archipelago unlawful.

Under the terms, Mauritius gains full sovereignty over the Chagos Archipelago, excluding Diego Garcia, which remains under joint UK-US jurisdiction.

The agreement includes provisions restricting foreign military presence on the islands.

Financial aspects of the deal comprise a £3.4 billion package over the lease term, additional annual payments of £45 million for 25 years to support Mauritian development, and a £40 million trust fund for displaced Chagossians.

The signing faced a temporary injunction from the UK High Court following a legal challenge by Chagossian citizens, citing exclusion from negotiations and concerns over resettlement rights.

The injunction was lifted, allowing the treaty to proceed.

Mauritian Prime Minister Navin Ramgoolam described the agreement as a significant step toward completing decolonization.

Conversely, some Chagossians and UK political figures criticized the deal for lacking guarantees on the right of return and for its financial implications.

The United States, a key stakeholder due to its military presence on Diego Garcia, endorsed the agreement, emphasizing the base's strategic importance for regional security operations.