The Longest Rivers in South America

South America is the 4th largest continent in the world by land area. While it is often considered to be its own continent, it is by some definitions a sub-continent of Americas. The continent has many notable features including Angel falls, the Amazon River (the longest river in the world), the Amazon Rainforest, the Atacama Desert and the Andes mountain range. South America is notable for being home to some of the most biodiverse places on Earth.

The 6 Longest Rivers in South America

1. The Amazon River

The 4,345 mile long Amazon River was considered to be the 2nd longest river in the world until recently, when some Peruvian and Brazilian studies confirmed that it is longer than the Nile. The most distant source of the Amazon is the Mantaro River in Peru. The Mantaro joins with other tributaries to form river Ucayali which meets with river Maranon to create the primary stem of the Amazon. The River Ene forms at the confluence of the River Apurimac and the River Mantaro, and it is part of the Amazon river’s headwaters which originates from Mismi. After about 450 miles, the Apurimac meets with river Mantaro and becomes Ene which joins River Perene and becomes river Tambo which drains to Ucayali. Ucayali-Tambo-Ene and Apurimac join the Amazon to form the longest river in the world. The Amazon has an average discharge of 209 million liters per second. The river's discharge represents about 20% of the world flow into the ocean. The Amazon River passes through multiple countries including Venezuela, Guyana, Ecuador, Colombia, Bolivia, Peru and Brazil.

2. Parana-Rio de la Plata

Situated in the southern central part of the continent, the Parana River runs through Argentina, Paraguay and Brazil for approximately 3,030 miles. The 3,030 mile long river is the 2nd longest river in South America, and it merges with the Rio-de-la-Plata (which is made up of the Uruguay and Paraguay rivers) before emptying into the Atlantic Ocean. It flows through Brazil, Uruguay, Bolivia and Argentina. Rio-de-la-Plata is part of the Uruguay-Argentina border and the host of these nations’ significant ports.

3. Tocantins-Araguaia

This 2,270 mile river is composed of two Brazilian rivers which are considered to be the tributaries of the Amazon (which is not the case). The Tocantins drains into the Atlantic alongside the Amazon. The Tocantins is a Tupi language term which refers to Toucan’s break while “Araguaia” refers to the River of macaws. The 3rd largest river in South America flows through numerous Brazilian states including Para, Maranhao, Goias, and Tocantins.

4. Madeira-Mamore-Grande-Caine-Rocha

The Mamore is a large river in Brazil and Bolivia which merges with Beni to create the Madeira. The Madeira, which is approximately 2,020 miles long, is the most significant Amazon tributary which accounts for over 15% of the Amazon water. The Rio Grande joins the Mamore through Ichillo River, one of its branches. Madeira-Mamore-Grande-Caine-Rocha merges to form a 2,100 mile river which is the 4th longest in South America. The Madeira-Mamore-Grande-Caine-Rocha flows through Peru, Bolivia and Brazil.

5. Purus River

The fifth longest river in South America is the Purus River. The Purus River is an Amazon River tributary with a drainage basin which is about 24,389 square miles. The 1,995 mile long river originates in Peru and helps define the Brazil-Peru boundary in Acre state before running along the border of the Santa Rosa-do-Purus national forest.

6. Sao Francisco

The Sao Francisco River is a 1,811 mile Brazilian river that is the 6th longest river in South America. Prior to colonization, the river was known as “Opava”. Sao Francisco rises from the mountain ranges of Canastra in Minas-Gerais state. Sao Francesco traverses through 5 Brazilian states before flowing into the Atlantic Ocean.

Which factors determine the length of the river?

Some of the factors that determine the length of a river include the source of the river and the scale of measurement and the definition of the river’s mouth. This is why the measurements of many rivers are mostly approximations, and this is the main reason for the dispute between the Amazon and the Nile over which is the longest river in the world. The Peruvian and Brazilian studies that confirmed that the Amazon is the world's longest river measured the river plus its connecting tidal and adjacent estuary.