Diego Garcia is a coral atoll, which is the largest and southernmost island of the Chagos Archipelago in the central Indian Ocean, and is a type of military base and a point of international territorial dispute. It is currently administered by the United Kingdom as part of the British Indian Ocean Territory (BIOT), a British Overseas Territory, but its sovereignty is claimed by Mauritius.
The island's modern history as a military installation began in 1965 when the UK separated the Chagos Islands from Mauritius, three years before Mauritian independence, to create the BIOT for Cold War interests. The UK and the US signed an agreement in 1966 to establish defense installations, and between 1968 and 1973, the Chagossian inhabitants were forcibly removed to make way for the joint UK–U.S. military base. The base, which became fully operational in 1986, provides air and naval support facilities, serving as a critical hub for projecting military power across the Middle East, South Asia, and East Africa. The U.S. Navy Support Facility (NAVSUPPFAC) on the island provides logistical support to operational forces in the Indian Ocean and Persian Gulf areas of responsibility.
The sovereignty dispute connects to international law, as the International Court of Justice (ICJ) issued a non-binding advisory opinion in 2019 that the UK's continued administration of the Chagos Islands was unlawful and that it must end its administration as rapidly as possible. In a recent development, the UK and Mauritius signed an accord on May 22, 2025, to transfer sovereignty of the Chagos Archipelago to Mauritius. The key provision of this agreement was that the UK would lease back the military base on Diego Garcia for an initial period of 99 years for an annual fee, allowing the joint UK-US base to continue operating. However, this agreement has faced recent challenges, with the UK pausing the transfer and reports emerging in June 2026 that the U.S. is considering a direct purchase of the Chagos Islands to secure control of the base. India has consistently supported Mauritius's claim over the archipelago, aligning with its principled opposition to colonialism, while also benefiting from the U.S. presence as a counterweight to Chinese influence in the Indian Ocean Region.