Brazil

Brazil has a dense and complex river system, one of the most extensive in the world, with eight major drainage basins flowing into the Atlantic.

An excerpt from the article 31 facts about Brazil

The main rivers are the Amazon River, the second longest (according to some, the longest in the world) and the largest in terms of water volume, Paran√° and its main tributary, the Iguacu (including Iguazu Falls), Rio Negro, Sao Francisco, Xingu, Madeira, and Tapajos.