Formosa is an island in the Bissagos Islands, Guinea-Bissau, part of the sector of Caravela. Its area is 140 km<sup>2</sup>, its length is 19.9 km and it is 10 km across at its widest. It forms practically one island with Ponta and Maio, separated by creeks. The island has a population of 1,873 (2009 census); the largest village is Abú.