Étang du Lanoux, Glacial lake in Angoustrine-Villeneuve-des-Escaldes, France.

Étang du Lanoux is the largest lake in the French Pyrenees, lying at 2,213 m in the Carlit massif on the commune of Angoustrine-Villeneuve-des-Escaldes. A concrete arch dam built from 1957 to 1960 raised it from 84 ha to 172 ha; the dam is 45 m high with a 176 m crest.

A natural lake of 84 hectares, it was raised by a concrete arch dam built between 1957 and 1960, growing to 172 hectares and 70.7 million cubic metres. France's plan to divert its waters to the Ariège led Spain to invoke the Treaty of Bayonne of 1866; the 1957 arbitration tribunal ruled in favour of France.

The name is Estany de Lanós in Catalan and Étang du Lanoux in French, as recorded by the Nomenclàtor toponímic de la Catalunya del Nord of the University of Perpignan. The IGN 1:25,000 map writes "Estany de Lanós ou Étang de Lanoux", while EDF, which operates the dam and hydroelectric works, uses étang du Lanoux. The ZNIEFF description of the "vallée du Lanoux" uses both lac du Lanoux and étang de Lanoux.

Reach this mountain lake by hiking through alpine trails that wind through the surrounding Carlit area. Weather conditions change quickly at high altitude, so bring protective gear and start early to make the most of daylight.

The concrete arch dam, built between 1957 and 1960, is 45 m high with a 176 m crest and a base 6 m thick, holding 25,000 m³ of concrete. It raised the lake from 84 ha and 20 million m³ to 172 ha and 70.7 million m³, with a maximum depth of 93 m.