Diego Garcia is the largest island of the Chagos Archipelago, it was handed over to Mauritius on 22 May 2025. 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 were a British overseas territory, but in early October 2024 the UK engaged in discussions with Mauritius aimed at transferring sovereignty of the islands. Following treaty ratification, sovereignty was formally transferred to Mauritius on May 22, 2025, while the military base remains under a 99-year lease.