Lac d'Aumar, Mountain reservoir in Hautes-Pyrénées, France

Lac d'Aumar is a mountain reservoir nestled in the Pyrenees at about 2,200 meters elevation. The water body covers roughly 25 hectares and creates a natural focal point in this high-altitude landscape.

The reservoir was built in 1901 to store water and support power generation in the region. This project was part of a broader effort to develop hydroelectric resources in the southern Pyrenees.

The name Aumar comes from the local term for "seawater", a reference to the lake's deep blue colour. Its south shore carries the GR 10 long-distance footpath between Barèges and the Lac de l'Oule, and the lake lies within the Néouvielle National Nature Reserve, created in 1936 and one of the oldest in France.

Access is via the D929 from Saint-Lary-Soulan through Tramezaïgues; at Fabian, a hamlet of Aragnouet, the D929 leaves the valley and climbs to Lac d'Orédon, then the D177 runs along Lac d'Aumar to Lac d'Aubert. The road is usually closed in winter, with signs at the Fabian crossroads. On the last stretch after Lac d'Orédon, uphill traffic is barred from 9:00 to 18:00 and reserved for service vehicles and the shuttle bus; the English source gives 9:30 to 18:00 from June to the end of September. The GR 10 long-distance trail runs along the south shore between Barèges and Lac de l'Oule.

Lac d'Aumar freezes for six months of the year, not solid ice but a long seasonal closure of the surface. It is a dimictic lake, mixing its waters twice a year, formed by glacial retreat and later slightly modified so water flows toward Lac d'Aubert and on to the Orédon dam, which feeds the Neste Canal.