Maldivian mariners knew of the Chagos Islands, which were known as Fōlhavahi in the northern Maldives and Hollhavai in the southern Maldives. Hollhavai also referred to other islands scattered throughout the Indian Ocean, such as the Seychelles. According to Southern Maldivian oral tradition, traders and fishermen were occasionally lost at sea and got stranded on one of the islands of the Chagos. Eventually they were rescued and brought back home. The
coconut crabs of the islands may have inspired Maldivian folklore about giant hermit crabs. These islands were judged to be too far away from the seat of the
Maldivian crown to be settled permanently. Thus for many centuries the Chagos were ignored.
Early settlement , 1787. The islands of the
Chagos Archipelago were charted by
Vasco da Gama in the early 16th century, and then claimed in the 18th century by France as a possession of Mauritius. They were first settled in the 18th century by African slaves and Indian contractors brought by Franco-Mauritians to found coconut plantations. At some point Diego Garcia hosted a
leper colony for patients from Mauritius, who were treated with turtle oil. In 1810, Mauritius was captured by the United Kingdom, and France subsequently ceded the territory in the
1814 Treaty of Paris. 's
Indian Navy Robert Moresby, 1837. The United Kingdom
abolished slavery in 1833, although those on what would become the BIOT continued work as
indentured labourers. In 1883 the plantations were bought by the Société Huilière de Diego et Peros. As of 1900, there were 426 families on the islands, 60 per cent descended from the original African-Malagasy slaves, and 40 per cent from South Asians brought over as indentured labour.
Chagossian creole developed as a common language. The lives of the inhabitants remained effectively controlled by the company, a system which persisted until the 1960s. An airstrip was built on Diego Garcia during the
Second World War, along with other military facilities. The military left once the war ended. In 1962 the plantations were bought by Chagos-Agalega Company, based in the Seychelles. At this time they covered . While it initially sought for the base to be given on a lease, Mauritius was eventually paid £3 million to compensate for the territory's separation, under pressure due to then-ongoing independence negotiations. Mauritius became an independent
Commonwealth realm in March 1968, and subsequently became a republic, also within the
Commonwealth, in March 1992.
Expulsion of the Chagossians signed by
D.A. Greenhill, 1966, relating to the
depopulation of the Chagos Archipelago.|alt= In April 1967, the British government purchased the privately owned
copra plantations for £600,000 and the Seychelles. The expulsion was carried out by preventing Chagossians who had left from returning from 1967, assisted by the Moulinie and Company (Seychelles), Limited company which the UK had set up to run the plantations. In 1968, when more workers were needed, non-Chagossian temporary workers were allowed in from the Seychelles. The remaining population was removed from Diego Garcia in January 1971, to meet a July 1971 deadline requested by the US. The populations of Peros Banhos and the Salomon Islands were removed starting from June 1972. The population as of 1965 was around 1,360 Chagossians, plus temporary workers from the Seychelles. Another few hundred Chagossians already lived outside of the islands. The UK informed the United Nations that BIOT had no indigenous population, meaning the UK would not have to
send reports on the territory to the UN. The island was strategically located near oil shipping routes, and Iran.
Development , showing military base. As of 1971, the population of Aldabra, Farquhar, and Desroches was 246. This dropped to 155 in 1975, likely reflecting uncertainty about these islands' future status. According to the CIA World Factbook, the Seychelles also had a sovereignty claim on the islands. In 1982, the UK and US agreed waste would be shipped away from the territory. During the
Gulf War, 20 nuclear-armed
Boeing B-52 Stratofortress bombers were stationed at the base as a
nuclear deterrent. Following the 2000 ruling the British government announced that Chagossians would be permitted to return to the archipelago, aside from Diego Garcia. This position was reversed in 2004, before any had moved. The United Kingdom offered citizenship to some Chagossians starting in 2002. On 23 May 2007, this was confirmed by the Court of Appeal. In a visit sponsored by the British government, the islanders visited Diego Garcia and other islands on 3 April 2006 for humanitarian purposes, including the tending of the graves of their ancestors. On 22 October 2008, the British government won an
appeal to the House of Lords regarding the
royal prerogative used to continue excluding the Chagossians from their homeland. In March 2007 Mauritian president
Anerood Jugnauth declared a willingness to take the dispute to the ICJ, and for Mauritius to leave the Commonwealth. In November 2007 a line of communication was established between the Foreign & Commonwealth Office and the Mauritian High Commission for BIOT-related matters. (That court's 2012 decision was not in favour of the Islanders anyway.) The protected area covered the territory's EEZ, but not its territorial waters. This arbitration was cited by Mauritius to halt an attempt by a coalition of NGOs to have the archipelago declared a World Heritage site in 2012. The base was seen as important for managing growing Chinese influence in the region. In February 2019, the ICJ issued an
advisory opinion by 13 votes to 1. On 22 May 2019, the UNGA adopted a resolution citing the ICJ advisory opinion, affirming that "the Chagos Archipelago forms an integral part of the territory of Mauritius". Votes against included the neighbouring Maldives, possibly concerned about the loss of maritime security benefits that emerge from the military base. The Seychelles benefits similarly, but voted for the resolution in solidarity with the African Union. China abstained in the 2019 UN vote, which was a step towards reaching an agreement to return the Chagos Archipelago to Mauritius. at Diego Garcia. On 28 January 2021, the United Nation's
International Tribunal for the Law of the Sea ruled, in a dispute between Mauritius and Maldives on their maritime boundary, that the United Kingdom has no sovereignty over the Chagos Archipelago, and that Mauritius is sovereign there. The United Kingdom disputes and does not recognise the tribunal's decision. As with the ICJ decision, this decision had no legal compulsion, although both contributed to international pressure on the UK. In February 2022, exiled islanders made their first unsupervised visit to an island in the Chagos Archipelago. The Permanent Representative of Mauritius to the United Nations,
Jagdish Koonjul, raised the Mauritian flag on
Peros Banhos. The main purpose of the 15-day Mauritian expedition is to survey the unclaimed
Blenheim Reef, to discover for a forthcoming
International Tribunal for the Law of the Sea hearing if it is exposed at high tide so is claimable. The chartered
Bleu De Nîmes was shadowed by a British fisheries protection vessel. In October 2021
Sri Lankan Tamil asylum seekers landed on Diego Garcia, and submitted asylum claims. The
Convention Relating to the Status of Refugees does not apply to the BIOT. Around 173 arrived in 2021 and 2022. Some were moved to
Rwanda, with around 60 left as of January 2024. In 2022, a dispute arising from American defence contractor
KBR allegedly prohibiting holidays during a period of low flight demand during the
COVID-19 pandemic led to 800
Overseas Filipino Workers being unable to leave Diego Garcia.
Post-ICJ negotiations and transfer Comparisons between the BIOT and occupied areas of Ukraine hindered British diplomatic efforts to obtain Ukrainian support following the
Russian invasion of Ukraine. Further pressure grew regarding Africa's "last colony", and in September 2022 British prime minister
Liz Truss met with Mauritian prime minister
Pravind Jugnauth The
Carnegie Endowment for International Peace has argued this change of approach is partly due to strategic shifts in US and UK foreign policies on Asia in response to China's growing power and influence, as disputes with former colonies encourage their deepening relationship with China. On 3 November 2022,
Patrick Wintour of
the Guardian reported that the UK and Mauritius had begun negotiations on sovereignty over the British Indian Ocean Territory, taking into account the international legal proceedings. These negotiations ceased in late 2023 after the UK Defence Secretary blocked the agreement that had been negotiated by the Foreign Office. Chagos Islanders would be allowed to return to the other islands and a fund will be established to support resettlement. No debate on the deal had taken place in the
Parliament of the United Kingdom due to it being in recess, and the deal attracted criticism from opposition politicians such as
James Cleverly, who, as foreign secretary, had initiated the negotiations that took place from November 2022 until December 2023. Some Chagossians have also criticised the deal for not having included the Chagossian community in the decision-making process. In November 2024 the Maldives reiterated a previous claim to the Chagos Islands, challenging ongoing negotiations between the UK and Mauritius. On 17 December 2024, newly elected Mauritius prime minister
Navin Ramgoolam, rejected the proposed agreement and asked for talks to reopen. Following resumed negotiations, a treaty was signed on 22 May 2025 that will transfer sovereignty to Mauritius once it comes into force (expected in late 2025), with Diego Garcia military base remaining under British control during a 99-year lease (the period can be extended by a further 40 years). However, in April 2026 the implementation of the agreement was put on an indefinite hold due to opposition from US President Donald Trump. The Government indicated that ratification of the agreement would not be sought in the current session of Parliament, with the former Permanent Under Secretary of State at the Foreign Office, Simon McDonald, commenting that "this agreement, this treaty will go into the deep freeze for the time being".
2026 resettlement attempt On 16 February 2026, four British
Chagossians landed on
Île du Coin in an attempt to establish a permanent settlement, without seeking government permission. Since the
expulsion of the Chagossians in 1971, no Chagossians have been allowed to live on the Chagos Islands. An injunction by the Chief Justice of the British Indian Ocean Territory three days later prevented the immediate deportation of the islanders. ==Responses to transfer of BIOT==