The Amazon River is the longest river in South America and flows through the world’s largest tropical rainforest. Its vast drainage basin covers parts of several countries, with most of the basin lying in Brazil.
The river begins from tributaries in the Andes and travels eastward to the Atlantic Ocean. Its exact length has been debated because researchers use different definitions for the river’s farthest source and main channel. Even so, the Amazon is universally recognized as one of Earth’s two longest rivers, alongside the Nile.
The Amazon has the greatest discharge of any river on Earth. At its mouth, it releases an enormous volume of freshwater into the Atlantic, influencing coastal waters and producing a plume that can be detected offshore. The river is also a major transportation route for communities across the basin.
The Amazon basin supports exceptional biodiversity, including thousands of fish species and numerous birds, mammals, reptiles, and plants. The river should not be confused with the Amazon rainforest: the river is the waterway, while the rainforest is the broader ecosystem surrounding its basin.