Huechulafquen Lake, Glacial lake in Neuquen Province, Argentina.

Huechulafquen Lake is a glacial lake in Neuquen Province within Lanin National Park, characterized by deep waters surrounded by steep mountain slopes. The lake forms part of a larger water system nestled beneath the Lanin Volcano in the Andean region.

Huechulafquen is a glacial lake fed by glaciers and meltwater streams from Lanín volcano. Around 1800 CE a lava flow from a cone of the Huanquihue Group reached the southern shore of its Epulafquén arm, building a rocky, distorted delta. Lakes Paimún and Epulafquén, its northern and southern arms, connect to the main body by short, narrow, shallow straits.

The name comes from Mapuche huechu (great) and laufquen (lake), though "lake of the tip" or "lake of the end" are also proposed. A road along the north shore passes through Mapuche communities living inside Lanín National Park. The lake's outflow forms the Chimehuin River at the "Boca del Chimehuin", one of Patagonia's main fly-fishing spots.

A road follows the northern shore past Mapuche communities inside Lanín National Park; another road runs along the southern shore of Lake Epulafquén to the Huanquihue lava flows and continues west to the Carirriñe Pass into Chile at 1,223 m. Annual precipitation drops from about 4,000 mm on the high mountains to about 1,400 mm at the eastern end, mostly in winter. Catamarans leave from Puerto Canoas toward Lake Epulafquén.

Around 1800 CE a lava flow from a cone of the Huanquihue Group reached the southern shore of Lake Epulafquén, the lake's southern arm, building a rocky, distorted delta still visible today. The group rises to 2,139 m above that shore.