Río Negro is the most important river of the Argentine province of Río Negro, and Patagonia in relation to its flow rate. Its name comes from the literal translation of the Mapuche term Curu Leuvu, although the water is more green than black. Formerly, it was also known as "river of the willows" because of the big number of weeping willows that grow along the bank. It's 635 km in length.
It originates from the junction of the Limay River and Neuquén River at the border with the Neuquén Province, and flows southeast to the Atlantic Ocean at 41.0223°S 62.7903°W, near El Cóndor beach resort some 30 km downstream from Viedma, Río Negro province's capital.
The river allows the Río Negro province to produce 65% of the pears and apples of Argentina. Besides irrigation, the river is also source of hydroelectricity with small dams on its course.
The river served as natural demarcation between "civilization" and the aboriginal territories during the Conquest of the Desert of late 19th century.