Rio Maranhão is a stream flowing through the state of Goiás, Brazil, situated within the upper Rio Tocantins basin. Positioned at approximately 14°34′S, 49°02′W, this waterway drains a region characterized by the rich biodiversity typical of central Brazilian river systems. The river is part of a broader network of tributaries feeding into the Rio Tocantins watershed, sharing its basin with the Rio das Almas and contributing to one of Brazil's most ecologically significant drainage systems. The surrounding landscape reflects the Cerrado biome, and the river supports a diverse assemblage of native fish species drawn from families including Characidae, Loricariidae, and others characteristic of the upper Tocantins drainage.