The Chagos Archipelago (/ˈtʃɑːɡoʊs/ or /ˈtʃɑːɡəs/) or Chagos Islands (formerly the Bassas de Chagas, and later the Oil Islands) is a group of seven atolls comprising more than 60 individual tropical islands in the Indian Ocean; situated some 500 kilometres (310 mi) due south of the Maldives archipelago. This chain of islands is the southernmost archipelago of the Chagos-Laccadive Ridge, a long submarine mountain range in the Indian Ocean. The Chagos also form a terrestrial ecoregion together with the Maldives and the Lakshadweep.