Nahuel Huapi Lake is a lake in the lake region of northern Patagonia between the provinces of Río Negro and Neuquén, in Argentina. The tourist center of Bariloche is on the southern shore of the lake.
The June 2011 eruption of the Puyehue-Cordón Caulle volcanic complex, in neighboring Chile, caused parts of the lake's surface to be blanketed in volcanic ash.
During the Last Glacial Maximum of the Llanquihue glaciation the lake basin was wholly occupied by a glacier.