The Three Brothers are a group of three small coral islands 20 kilometres (12 miles) east of Eagle Islands along the central western rim of the Great Chagos Bank, which is the world's largest coral atoll structure, located in the Chagos Archipelago.

The individual islands are, from north-west to south-east:

• North Brother or Île du Nord (6 ha; 15 acres)
• Middle Brother or Île du Milieu (8 ha; 20 acres)
• Resurgent Island (1 ha; 2½ acres)
• South Brother or Île du Sud (23 ha; 57 acres)
• Pangus Island (55 ha; 90 acres)

Discovered by the Portuguese, by Vasco da Gama, the islands were known as Bassas de Chagos. In 1975 during the Joint Services Expedition to Danger Island (JSDI), the expedition members were taken by RFA Resurgent to Eagle Islands, then by ketch and inflatable craft to Danger Island, and then to Three Brothers. The expedition made a topographical survey of the coral reefs, an ecological survey of the Pangus corals on it, and a study on the metabolism of the reef. A reference collection of samples of the flora and fauna of the area was also undertaken. Small, rocky Resurgent Island emerged after the naming of the Three Brothers, and was named after the RFA Resurgent, which supported the 1975 Danger Island scientific research expedition to the area.

Since 1998 the islands have been part of the Chagos Archipelago Strict Nature Reserve. It is forbidden to land on the islands or anchor a boat nearby. The islands have large populations of nesting seabirds, including brown noddies, lesser noddies, sooty terns and Audubon's shearwaters.

• World's largest marine reserve created
• Joint Services Expedition To Danger Island - (1975) commemorative postcard
• Chagos research papers and books
• Opisthobranch molluscs from the Chagos Archipelago, Central Indian Ocean

06°09′S 71°31′E / 6.150°S 71.517°E / -6.150; 71.517 (Three Brothers)