Certascan Lake, Glacial lake in Lladorre, Spain.

Certascan Lake is a glacial lake at 2,236 m in the head of the Cardós valley, in Lladorre (Pallars Sobirà), east of the 2,853 m Certascan peak. It covers 47 hectares, reaches a maximum depth of 96 m and holds 16 hm³, making it the largest lake in the Catalan Pyrenees. Its outflow forms the Certascan river, and the Certascan mountain refuge stands nearby.

The lake formed through glacial action in ancient times and later became part of regional infrastructure development. In 1974 a hydroelectric power station was built in the Tavascan area, connecting the water system to the regional electricity grid.

The lake lies within the Alt Pirineu Natural Park, and its outflow feeds the Certascan river, which joins the Lladorre. Since 1974 water is diverted through an underground channel to the Tavascan hydroelectric station. The Certascan mountain refuge stands near the shore, a stopping point on the trails of the Cardós valley.

The lake sits at 2,236 m at the head of the Cardós valley, near Lladorre, and the Certascan mountain refuge stands close to its shore. Access is on foot via marked trails; the climb is sustained and calls for good fitness and footwear. Camping and fires are not allowed in this protected zone of the Alt Pirineu Natural Park.

The lake's outflow forms the Certascan river, which joins the Lladorre; in Spanish sources the same water is described as feeding the Noguera de Cardós, which meets the Noguera Pallaresa at Llavorsí. Since 1974 a subterranean channel has diverted water to the Tavascan hydroelectric station, inaugurated that year.