Cantão is a tropical forest ecosystem located in the central Araguaia river basin, the southeastern edge of the Amazon biome, in the Brazilian state of Tocantins. It is one of the biologically richest areas of the eastern Amazon, with over 700 species of birds, nearly 300 species of fish (more than in all of Europe), and large populations of endangered species such as the giant otter and the black cayman. About 90% of the Cantão ecosystem is protected within Cantão State Park.