Diego Garcia is an atoll of the Chagos Archipelago, just south of the equator. It is the island with the largest landmass in the archipelago. Today, the archipelago is the only settled place in the British Indian Ocean Territory. The Portuguese discovered it, and the French settled it in the 1790s. It used to be part of Mauritius. After the Napoleonic Wars, Mauritius became a British colony. Diego Garcia is 733 kilometres (455 mi) south of Gan Island, the southernmost island of the Maldives. It is 1,863 kilometres (1,158 mi) east of Paislin island of the Seychelles. The archipelago is claimed by Mauritius, but controlled by the British. The United States run a military base on the island.
The archipelago has a landmass of about 27 square kilometres (10 sq mi), the lagoon has an area of about 174 square kilometres (67 sq mi). In 2021, about 4,200 people, all of them military personnel lived on Diego Garcia. There is an airport, and a small harbor on the island. Communication is done using satellite.