Diego Garcia () is the largest island of the Chagos Archipelago. It has been used as a joint UK–U.S. military base since the 1970s, following the expulsion of the Chagossians by the UK government. The Chagos Islands are a British overseas territory, though a treaty to transfer sovereignty from the UK to Mauritius was signed on 22 May 2025, with a provision that the military base at the island would remain under British control for at least 99 years. The agreement may be renewed for an additional 40 years after the initial 99-year period, and for an additional period thereafter. The UK government expected the treaty to be ratified sometime in 2026. The UN Committee on the Elimination of Racial Discrimination has expressed "deep concern" at the terms of the deal.
Located just south of the equator in the central Indian Ocean, Diego Garcia lies east of Tanzania, east-southeast of Somalia, south of the Maldives, southwest of India, west-southwest of Sumatra, northwest of Australia, and northeast of Mauritius Island. Diego Garcia is part of the Chagos–Laccadive Ridge, an underwater mountain range that includes the Lakshadweep, the Maldives, and the other 60 small islands of the Chagos Archipelago. The island observes UTC+6 year-round.
Diego Garcia was discovered by Portuguese sailors in 1512 and remained uninhabited until the French began using it as a leper colony and for coconut plantations in the late 18th century. After the Napoleonic Wars, the island was transferred to British control. It remained part of Mauritius until 1965, when it became part of the newly formed British Indian Ocean Territory (BIOT).
In 1966, Diego Garcia had a population of 924, mostly contract workers employed in coconut plantations. However, between 1968 and 1973, the Chagossian inhabitants were forcibly removed to make way for the military base. In 2019, the International Court of Justice issued a non-binding advisory opinion that the decolonisation of Mauritius had not been lawfully completed when it gained independence in 1968, and that the UK was "under an obligation to end its administration of the Chagos Archipelago as rapidly as possible". The United Nations General Assembly later voted overwhelmingly in favour of a resolution endorsing this opinion and calling on the UK to end its administration, though the UK has dismissed the ruling as non-binding.
Until the resettlement of Île du Coin, Diego Garcia remained the only inhabited island of the BIOT, with a population of around 4,000 consisting predominantly of military personnel. It is one of two critical U.S. bomber bases in the Indo-Pacific region, alongside Andersen Air Force Base in Guam. It is nicknamed the "Footprint of Freedom" by the U.S. Navy due to its shape and strategic location in the Indian Ocean.
History
Before European arrival
No tangible evidence exists of people on Diego Garcia before the arrival of Europeans. There is speculation about visits during the Austronesian diaspora around AD 700, as some say the old Maldivian name for the islands originated from Malagasy. Arabs, who reached Lakshadweep and Maldives around AD 900, may have visited the Chagos. Southern Maldivian oral tradition tells of occasional traders and fishermen marooned on, and later rescued from, Foalhavahi () Chagos. Golāvahi (often spelled Golavahi or Golavohi) is also an ancient Maldivian (Dhivehi) name used in old historical texts, such as the Raadhavalhi, to refer to present-day Diego Garcia, while Golāvehi refers to the people of Golāvahi.
European arrival The uninhabited islands were discovered by the Portuguese navigator, explorer, and diplomat Pedro Mascarenhas in 1512, first named as Dom Garcia, in honour of his patron, Dom Garcia de Noronha when he was detached from the Portuguese India Armadas during his voyage of 1512–1513. Another Portuguese expedition with a Spanish explorer, Diego García de Moguer, rediscovered the island in 1544 and named it after himself. Garcia de Moguer died the same year on the return trip to Portugal in the Indian Ocean, off the South African coast. It is assumed that the island was named after one of its first two discoverers—the one by the name of Garcia, the other with name Diego. Also, a cacography of the saying (literally 'Thank God') is eligible for the attribution of the atoll. Although the Cantino planisphere (1504) and the Ruysch map (1507) clearly delineate the Maldive Islands, giving them the same names, they do not show any islands to the south which can be identified as the Chagos archipelago.
The Sebastian Cabot map (Antwerp 1544) shows a number of islands to the south which may be the Mascarene Islands. The first map which identifies and names "Los Chagos" (in about the right position) is that of Pierre Desceliers (Dieppe 1550), although Diego Garcia is not named. An island called "Don Garcia" appears on the of Abraham Ortelius (Antwerp 1570), together with "Dos Compagnos", slightly to the north. It may be the case that "Don Garcia" was named after Garcia de Noronha, although no evidence exists to support this. The island is also labelled "Don Garcia" on Mercator's Nova et Aucta Orbis Terrae Descriptio ad Usum Navigatium Emendate (Duisburg 1569). However, on the of Jodocus Hondius (London 1589), "Don Garcia" mysteriously changes its name to "I. de Dio Gratia", while the "I. de Chagues" appears close by.
The first map to delineate the island under its present name, Diego Garcia, is the World Map of Edward Wright (London 1599), possibly as a result of misreading Dio (or simply "D.") as Diego, and Gratia as Garcia. The of Hendrik Hondius II (Antwerp 1630) repeats Wright's use of the name, which is then proliferated on all subsequent Dutch maps of the period, and to the present day.
Settlement of the island Diego Garcia and the rest of the Chagos islands were uninhabited until the late 18th century. In 1778, the French Governor of Mauritius granted Monsieur Dupuit de la Faye the island of Diego Garcia, and evidence exists of temporary French visits to collect coconuts and fish.Edis (2004), p. 29. Several Frenchmen living in "a dozen huts" abandoned Diego Garcia when the British East India Company attempted to establish a settlement there in April 1786. The supplies of the 275 settlers were overwhelmed by 250 survivors of the wreck of the British East Indian Ship Atlas in May, and the colony failed in October.Edis (2004), p. 32. Following the departure of the British, the French colony of Mauritius began marooning lepers on the island, and in 1793, the French established a coconut plantation using slave labour, which exported cordage made from coir (coconut fibre), and sea cucumbers as a far-eastern delicacy.Edis (2004), p. 33.
Diego Garcia became a colony of the UK after the Napoleonic Wars as part of the Treaty of Paris (1814), and from 1814 to 1965 it was administered from Mauritius; the main plantations were at East Point, the main settlement, Minni Minni, north of East Point, and Pointe Marianne, on the western rim, all on the lagoon side of the atoll. The workers lived at each and at villages scattered around the atoll.
From 1881 until 1888, the atoll hosted two coaling stations for steamships crossing the Indian Ocean.D. R. Stoddart (1971): "Settlement and development of Diego Garcia". In: Stoddart & Taylor (1971), pp. 209–218.
In 1882, the French-financed, Mauritian-based (the 'Oilmaking Company of Diego and Peros'), consolidated all the plantations in the Chagos under its control.
20th century
In 1914, the island was visited by the German light cruiser halfway through its commerce-raiding cruise during the early months of World War I.
In 1942, the British opened RAF Station Diego Garcia and established an advanced flying boat unit at the East Point Plantation, staffed and equipped by No. 205 and No. 240 Squadrons, then stationed on Ceylon. Both Catalina and Sunderland aircraft were flown during the course of World War II in search of Japanese and German submarines and surface raiders. At Cannon Point, two naval guns were installed by a Royal Marines detachment. In February 1942, the mission was to protect the small Royal Navy base and Royal Air Force station located on the island from Japanese attack. Operation of the guns was later taken over by Mauritian and Indian Coastal Artillery troops.Edis (2004), p. 73. Following the conclusion of hostilities, the station was closed on 30 April 1946.Edis (2004), p. 70.
In 1962, the Chagos Agalega Company of the British colony of Seychelles purchased the Société Huilière de Diego et Peros and moved company headquarters to Seychelles.Edis (2004), p. 82.
In the early 1960s, the UK was withdrawing its military presence from the Indian Ocean, not including the airfield at RAF Gan to the north of Diego Garcia in the Maldives (which remained open until 1976), and agreed to permit the United States to establish a naval communication station on one of its island territories there. The United States requested an unpopulated island belonging to the UK to avoid political difficulties with newly independent countries, and ultimately the UK and United States agreed that Diego Garcia was a suitable location.Sand (2009), p. 3.
Purchase by the United Kingdom
To accomplish the UK–US mutual defence strategy, in November 1965, the UK purchased the Chagos Archipelago, which includes Diego Garcia, from the then self-governing colony of Mauritius for £3 million to create the British Indian Ocean Territory (BIOT), with the intent of ultimately closing the plantations to provide the uninhabited British territory from which the United States would conduct its military activities in the region.
In April 1966, the British government bought the entire assets of the Chagos Agalega Company in the BIOT for £600,000 and administered them as a government enterprise and immediately leased the plantations back to Chagos Agalega while awaiting United States funding of the proposed facilities, with an interim objective of paying for the administrative expenses of the new territory. However, the plantations, both under their previous private ownership and under government administration, proved consistently unprofitable due to the introduction of new oils and lubricants in the international marketplace, and the establishment of vast coconut plantations in the East Indies and the Philippines and the company terminated the lease at the end of 1967.
On 30 December 1966, the United States and the UK executed an agreement through an Exchange of Notes which permitted the United States to use the BIOT for defence purposes for 50 years until December 2016, followed by a 20-year extension (to 2036) as long as neither party gave notice of termination in a two-year window (December 2014 – December 2016) and the UK may decide on what additional terms to extend the agreement."Report: The use of Diego Garcia by the United States ". UK Parliament, September 2014 No monetary payment was made from the United States to the UK as part of this agreement or any subsequent amendment. Rather, the United Kingdom received a US$14-million discount from the United States on the acquisition of submarine-launched Polaris missiles per a now-declassified addendum to the 1966 agreement.Sand (2009), pp. 6–8.
Arrival of the U.S. Navy