Nelson Island or Legour Island is the northernmost and the easternmost island of the Great Chagos Bank, which is the world's largest coral atoll structure, located in the Chagos Archipelago in the Indian Ocean. The nearest neighbour is Île Boddam in the Salomon Islands. This lonely island was discovered by a French explorer, Alexis Legour, in 1820. It seems to have been always uninhabited, even between the 17th and the 20th century when there were coconut plantations in other islands of the Chagos. Thanks to its remoteness there has always been a numerous population of sea turtles in this island. Nelson Island has been identified as an Important Bird Area by BirdLife International. Birds for which the island is of conservation significance include lesser noddies and brown noddies.