Bananal Island (, ) is a large river island formed from the bisection of the Araguaia River, in southwestern Tocantins, Brazil. The island is formed by a fork in a very flat section of the Araguaia; the western stream of the fork retains the name Araguaia and the eastern one is called the Javaés River. By reuniting later, both streams form Bananal Island, which is the second largest river island in the world and the largest without an ocean coastline, at long and wide.