The
Rio Negro ( ; "
Black River") is the largest left
tributary of the
Amazon, the largest
blackwater river in the world, and one of the world's ten largest rivers in average discharge. It has its sources along the watershed between the
Orinoco and the Amazon basins, and also connects with the Orinoco by way of the
Casiquiare canal in southern
Venezuela. In Colombia, where the Rio Negro's sources are located, it is called the
Guainía River. Its main affluent is the
Vaupés, with sources near the headwaters of the
Guaviare branch of the
Orinoco, the drainage of the eastern slope of the
Andes of
Colombia. The Rio Negro joins with the Rio Solimões to form the Amazon River south of
Manaus,
Brazil.