Diego Garcia is not a U.S. territory. The coral atoll, which is located in the central Indian Ocean, is administered by the United Kingdom as part of the British Indian Ocean Territory since 1965, after its separation from Mauritius. In the late 1960s and early 1970s, the island’s civilian population was removed to allow for the development of a military base operated by the United States and the United Kingdom.
The legality of the separation has been widely contested, and a treaty to transfer sovereignty from the United Kingdom to Mauritius was signed in May 2025. However, it requires ratification by both countries. As part of the deal, the United Kingdom would have a 99-year lease on the base.