What is the longest river in South America?

The Amazon River is the longest river in South America. It flows through Peru, Colombia, and Brazil before emptying into the Atlantic Ocean, crossing a continent-sized basin that supports the world’s largest tropical rainforest.

The river is also the world’s largest by water discharge, releasing more water than any other river. Its enormous system includes major tributaries such as the Rio Negro, Madeira, Tapajós, Ucayali, and Marañón. Depending on which headwater and mouth are chosen, published length estimates vary, but no competing South American river approaches its continental scale.

The Amazon’s source has been debated because the upper network contains several long Andean tributaries. Some studies identify the Apurímac drainage, while others point to the Mantaro system as the most distant source. These measurement disputes do not change its status as South America’s longest river.

The Paraná, Orinoco, and São Francisco are major South American rivers, but each is substantially shorter. The Amazon is also often confused with the Amazon basin, which is the much larger drainage area feeding the river.