The Chagos contain the world's largest coral atoll, The Great Chagos Bank, which supports half the total area of good quality reefs in the Indian Ocean.
The largest individual islands are Diego Garcia (32.5 km2), Eagle (Great Chagos Bank, 3.1 km2), Île Pierre (Peros Banhos, 1.40 km2), Eastern Egmont (Egmont Islands, 2.17 km2), Île du Coin (Peros Banhos, 1.32 km2) and Île Boddam (Salomon Islands, 1.27 km2).