The Neuquén River (Spanish: Río Neuquén) is the second most important river of the province of Neuquén in the Argentine Patagonia, after the Limay River.
The river begins in the northwest of the province at an elevation of 2,300 metres (7,500 ft), to be fed by a number of streams through valleys of the lower Andes while advancing diagonally in southeast direction. Among these streams, some of them from draining of small lakes, are the Trocomán, Reñi Leuvü, Agrio and Nahueve. Further down, its main tributaries are the rivers Varvarco, and Agrio, who provides almost a third of the Neuquén flow. Along its way the river receives some sediments from volcanoes Copahue and Domuyo that might sometimes affect the clarity of the otherwise clean waters.
After meeting the Agrio, the Neuquén river has no natural lakes that could regulate its flow, which results in sharp raises of level during thawing and rainy periods. A derivative channel towards the Pellegrini Lake in Río Negro Province has been built to compensate for abrupt changes in the flow, as well as the Cerros Colorados Complex, also used to generate hydroelectricity.
The average flow of the river is of 308 cubic metres per second (10,900 cu ft/s) (measured at Paso de Indios), and its drainage basin covers about 50,774 square kilometres (19,604 sq mi). At its mouth at 38°59′34″S 68°00′06″W / 38.9927°S 68.0017°WCoordinates: 38°59′34″S 68°00′06″W / 38.9927°S 68.0017°W, the Neuquén meets the Limay River near the city of Neuquén, to form the Río Negro, which continues its way east towards the Atlantic Ocean.