Amazon River. The Amazon River (UK: , US: ; Spanish: R??o Amazonas, Portuguese: Rio Amazonas) in South America is the largest river by discharge volume of water in the world, and the longest or second-longest river system in the world, a title which is disputed with the Nile. The headwaters of the Apur??mac River on Nevado Mismi had been considered, for nearly a century, the Amazon basin's most distant source until a 2014 study found it to be the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru. The Mantaro and Apur??mac rivers join, and with other tributaries form the Ucayali River, which in turn meets the Mara????n River upstream of Iquitos, Peru, forming what countries other than Brazil consider to be the main stem of the Amazon. Brazilians call this section the Solim??es River above its confluence with the Rio Negro forming what Brazilians call the Amazon...