Which river has the largest drainage basin by area?

The Amazon River has the largest drainage basin by area, covering roughly 7 million square kilometres across South America.

Its basin extends through Brazil, Peru, Colombia, Bolivia, Ecuador, Venezuela, and Guyana, draining about 40% of the continent. Thousands of tributaries feed the system, including the Rio Negro, Madeira, Japurá, Purus, Xingu, and Ucayali. The basin is also the source of the enormous seasonal floods that sustain the Amazon rainforest and its várzea floodplain forests.

A common mix-up is confusing drainage-basin size with river length or water volume. The Amazon is the world’s largest river by discharge, but its claim to being the longest river is disputed with the Nile. Basin measurements can also vary depending on whether connected waterways such as the Tocantins are included, but the Amazon basin remains decisively the world’s largest.