The Tocantins River is a river in Brazil, the central fluvial artery of the country. In the Tupi language, its name means "toucan's beak". It runs from south to north for about 2,450 km. It is not really a branch of the Amazon River, since its waters flow into the Atlantic Ocean alongside those of the Amazon. It flows through four Brazilian states and gives its name to one of Brazil's newest states, formed in 1988 from what was until then the northern portion of Goiás.

The Amazon River in South America is the largest river by discharge volume of water in the world, and the longest or second-longest river system in the world, a title which is disputed with the Nile.