Nahuel Huapi Lake is an Andean lake in the lake region of northern Patagonia between the provinces of Río Negro and Neuquén, in Argentina. The lake has a northwest-southeast elongated shape and complex geography with several branches, peninsulas and islands. The city of Bariloche is on the southern shore of the lake and the town of Villa La Angostura lies on its northwestern shores. The lake is wholly inside Nahuel Huapi National Park. It is one of the largest lakes in northern Patagonia. It is drained by Limay River and it is part of the watershed of Negro River which discharges into the South Atlantic.

Patagonia is a geographical region that encompasses the southern end of South America, governed by Argentina and Chile. The region comprises the southern section of the Andes Mountains with lakes, fjords, temperate rainforests, and glaciers in the west and deserts, tablelands, and steppes to the east. Patagonia is bounded by the Pacific Ocean on the west, the Atlantic Ocean to the east, and many bodies of water that connect them, such as the Strait of Magellan, the Beagle Channel, and the Drake Passage to the south.