Diego Garcia is an atoll located south of the equator in the central Indian Ocean. Diego Garcia is the largest of the 60 small islands comprising the Chagos Archipelago. Diego Garcia was settled by the French in the 1790s and was transferred to British rule after the Napoleonic Wars. It was one of the "Dependencies" of the British Colony of Mauritius until it was detached for inclusion in the newly created British Indian Ocean Territory (BIOT) in 1965. Between 1968 and 1973, the population of the BIOT was removed to Mauritius and The Seychelles, following which the United States built a large naval and military base on Diego Garcia, which has been in continuous operation ever since. As of March 2015, Diego Garcia is the only inhabited island of the BIOT; the population is composed of military personnel and supporting contractors.

The atoll is located 3,535 km (2,197 mi) east of Tanzania's coast, 1,796 km (1,116 mi) south-southwest of the southern tip of India (at Kanyakumari) and 4,723 km (2,935 mi) west-northwest of the west coast of Australia (at Cape Range National Park, Western Australia). Diego Garcia lies at the southernmost tip of the Chagos-Laccadive Ridge, a vast submarine mountain range, top of coral reefs, atolls, and islands comprising Lakshadweep.

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