São Luís Island also known as Upaon-açu Island or Maranhão Island is an island in state of Maranhão, Brazil with an area of 1,410 km², located between the Baía de São Marcos and the Baía de São José. There are 4 cities located in the island: São Luís, after which the island is named, São José de Ribamar, Paço do Lumiar, and Raposa. The city of São Luís also covers three more minor islands, Tauá Mirim, Tauá, and Medo. Raposa also has an island. The population of these 4 cities in July 2013 IGBE estimate is 1,366,266, up from 1,309,330 in the 2010 Census.
São Luís is the capital of the state. The Island was originally named Upaon-Açu by the Native inhabitants of the island. It is in the top 50 on the list of islands by population.