The entire land area of the islands is a mere 63 km², with the largest island, Diego Garcia, having an area of 44 km². There are five other main island groups: Peros Banhos, the Salomon Islands, the Eagle Islands, the Egmont Islands, and the Three Brothers. Isolated islands include Nelsons Island and Danger Island.

The islands were discovered by Vasco da Gama in the early sixteenth century, then claimed in the eighteenth century by France as a possession of Mauritius. The United Kingdom gained possession of both Mauritius and the archipelago in 1814, and retained the islands as part of the British Indian Ocean Territory when Mauritius gained independence. Since 1976, the archipelago has been coterminous with the British Indian Ocean Territory, but it is also claimed by Seychelles.

Although there was no pre-European population, a few hundred people of mostly Indian descent known as the Ilois lived on the islands for several hundred years until they were expelled to Mauritius by the British Government between 1967 and 1973. Currently, the only habitation is a joint US-UK naval support facility on Diego Garcia. Other unhabited islands, especially in the Salomon group, are common stopping points for long-distance sailors travelling from Southeast Asia to the Red Sea or the coast of Africa.

The British Government instituted an investigation into relocating the former islanders to some of the uninhabited islands, but concluded that this was impossible due to a lack of fresh water. This is disputed by the former islanders, who point out that rainfall in the archipelago is among the highest in the world.

See also

• List of Islands in Chagos Archipelago