British Indian Ocean Territory

The British Indian Ocean Territory (BIOT) is a British Overseas Territory situated in the Indian Ocean. The territory comprises the seven atolls of the Chagos Archipelago with over 1,000 individual islands, many very small, amounting to a total land area of 60 square kilometres (23 square miles).^[6] The largest and most southerly island is Diego Garcia, 27 square kilometres (10 square miles), the site of a Joint Military Facility of the United Kingdom and the United States.^[7] Official administration is remote from London,^[8][9] though the local capital is often regarded as being on Diego Garcia.^[10]

Mauritius claimed that the British government separated the Chagos Archipelago from Mauritius, creating a new colony, the British Indian Ocean Territory (BIOT). However, this was disputed by the United Kingdom, who said that the Chagos Islands had no historical or cultural ties to Mauritius, and that they were only governed during the colonial period from Mauritius (2191 km or 1361 miles away) as an administrative convenience. Mauritius further claimed that to avoid accountability to the United Nations for its continued colonial rule, the UK falsely claimed that the Chagos had no permanent population.^[11]

The only inhabitants are British and United States military personnel, and associated contractors, who collectively number around 3,000 (2018 figures).^[6] The forced removal of Chagossians from the Chagos Archipelago occurred between 1968 and 1973. The Chagossians, then numbering about 2,000 people, were expelled by the British government to Mauritius and Seychelles, even from the outlying islands far away from the military base on Diego Garcia. Today, the Chagossians are still trying to return, but the British government has repeatedly denied them the right of return despite calls from numerous human rights organisations to let them.^[12][13] The islands are off-limits to Chagossians, tourists, and the media.

Since the 1980s, the Government of Mauritius sought to gain control over the Chagos Archipelago, which was separated from the then Crown Colony of Mauritius by the UK in 1965 to form the British Indian Ocean Territory. A February 2019 advisory opinion of the International Court of Justice called for the islands to be given to Mauritius. Afterward, both the United Nations General Assembly and the International Tribunal for the Law of the Sea reached similar decisions. Negotiations between the UK and Mauritius began in November 2022, and culminated in an October 2024 understanding that the UK would cede the territory to Mauritius for possible resettlement while retaining the joint US-UK military base on Diego Garcia.^[14] However, newly elected Mauritius prime minister Navin Ramgoolam rejected the proposed agreement and asked for talks to reopen in December 2024.^[15] Following resumed negotiations a treaty was signed on 22 May 2025 that will formally transfer the sovereignty of the territory to Mauritius once it comes into effect, while the Diego Garcia military base remains under British control during a 99-year lease.^[16][17] The UK government expects the treaty to be ratified near the end of 2025.^[18]

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