Llancanelo Lake, Wetland nature reserve in Malargüe Department, Mendoza Province, Argentina

Llancanelo Lake is a salt lake in the Malargüe Department of Mendoza Province, Argentina, 75 km from the city of Malargüe at 1,280 m above sea level. It lies in an arid region near the Andes, on the boundary between Cuyo and Patagonia. Fed mainly by the Malargüe River and several streams, it has a triangular shape when seen from above.

The lake was recognized in 1995 as a wetland of international importance and given protected status. This designation acknowledged its role as a vital ecosystem in Argentina's southern region.

The name Llancanelo combines yanca, the quartz used to make arrowheads, and nelo, greenish-blue, describing the triangular lake seen from above as an arrowhead. Huarpes and Puelches hunted and fished here before the Conquest of the Desert; the reserve was created in 1980.

The reserve lies about 75 km from Malargüe city, at 1,280 m above sea level, reached by road from Malargüe. Waterfowl censuses counted up to 200,000 birds in summer and 60,000 in winter, so the austral summer brings the largest concentrations. The lake is saline and the surrounding steppe is arid; carry water, sun protection and windproof clothing.

The first scientific surveys, led by Raúl Aramburu of the Universidad de La Plata in 1983, established the area's faunal wealth; Heber Sosa later completed a bird inventory of about 155 species. From 1990, waterbird censuses counted up to 200,000 individuals in summer and 60,000 in winter, figures later confirmed and even increased.