Uruguay

Uruguay River rises in Brazil's Serra do Mar, where the Canoas and Pelotas rivers meet and runs a long way before emptying its waters in Rio de la Plata. Below the river channel, the Uruguay River forms a submerged canyon with a depth of over 300 feet. The river also includes five international bridges, two of which connect Argentina and Brazil and the other three which connect Argentina and Uruguay. Argentina and Uruguay were at odds over the development of pulp mills along the river, with Argentina alleging that Uruguay had violated a 1975 deal. All matters concerning the river were intended to be agreed upon by both countries, according to the treaty.

The river's name is believed to be derived from the Spanish settlers' interpretation of the Guaran language word that the locals used to refer to it. "The river of the uru (an indigenous bird)" and "(river of) the uruguá" are two possible interpretations.

Length: 1,142 miles (shared with Brazil and Uruguay)