Bananal Island (Portuguese: Ilha do Bananal, IPA: [banaˈnaw]) 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 River. Bananal Island is the second largest fluvial island in the world, at 350 km (217 mi) long and 55 km (34 mi) wide.