The Amazon River is the largest river in the world by discharge volume and one of the longest, with a length estimated between 6,400 and 7,000 kilometers. It is responsible for approximately 20% of the total freshwater discharge into the world’s oceans. This immense waterway sustains the planet’s largest rainforest ecosystem, covering millions of square kilometers. Its scale makes it a central feature of South America’s geography.
The Three Nations the River Flows Through
The main stem of the Amazon River flows through only three South American nations: Peru, Colombia, and Brazil. The river’s journey begins in Peru, where its headwaters collect in the Andes Mountains. In its upper reaches, the river is often referred to as the Marañón and Ucayali before their confluence forms the internationally recognized Amazon.
The river passes through a short section near the point where the borders of all three countries meet, known as the Tres Fronteras (Three Borders). This tri-border region connects the Colombian town of Leticia, the Brazilian town of Tabatinga, and the Peruvian community of Santa Rosa. The vast majority of the river’s length and volume are contained within Brazil, where it is locally called the Solimões River until its confluence with the Rio Negro near Manaus.
Source and Mouth of the Amazon
The source of the Amazon River system is found high in the Andes Mountains of Peru. Current scientific consensus points to the headwaters of the Mantaro River or the Apurímac River system, specifically the Carhuasanta Creek near Nevado Mismi, as the farthest continuous source. This starting point is found at an elevation of over 5,000 meters and is surprisingly close to the Pacific Ocean, though the water travels thousands of kilometers eastward.
The river culminates at the Atlantic Ocean on the northeastern coast of Brazil. The Amazon does not empty into a single channel but rather a vast, complex estuary. The immense volume of water discharged means the river’s brown, sediment-laden waters can be detected over 100 kilometers out to sea. The mouth is characterized by a massive delta that includes the large Marajó Island, with water flowing out through multiple channels.
Clarifying the Amazon Basin
A common geographical confusion exists between the main Amazon River channel and the much larger Amazon Drainage Basin. While the main river flows through only three countries, the massive drainage basin, which collects water from all its tributaries, extends across nine different nations. This basin is the largest in the world, covering approximately 7 million square kilometers.
The tributaries and their watersheds include significant portions of Bolivia, Ecuador, Venezuela, Guyana, Suriname, and French Guiana, in addition to the three countries the main river traverses. The waters from these six nations flow into the Amazon via thousands of tributaries, such as the Madeira and Putumayo Rivers, but the central channel never crosses their borders.