Hourtin-Carcans Lake, Freshwater lake in Gironde, France

Hourtin-Carcans Lake stretches 18 km north to south, parallel to the Atlantic, and is up to 5 km wide, with a surface area of 5,667 hectares that stays the same in all seasons. Its dune shores were fixed with pine plantations in the 19th century, and it links to the Étang de Lacanau via the Canal des Étangs.

American forces established a seaplane base at Contaut in 1917 on the northern edge during World War I. The installation was later converted into a French naval training facility that shaped regional development.

Residents of Hourtin to the north call it the lac d'Hourtin, those of Carcans to the south call it the lac de Carcans, and in Occitan it is the lac de Hortin e de Carcan. The lake borders the Médoc, and the resort of Maubuisson sits on its southwestern shore. Claude Miller shot scenes of Thérèse Desqueyroux on its banks.

The lake lies parallel to the Côte d'Argent, with Hourtin to the north-east, Carcans to the south-east and the resort of Maubuisson on the south-western shore. The canal des Étangs links it to the étang de Lacanau. Its surface area stays at 5,667 hectares in all seasons, so water levels do not vary with the seasons.

Its surface area of 5,667 hectares stays the same in every season, so the lake is not larger in winter and smaller in summer. By comparison, Lac de Grand-Lieu in Loire-Atlantique grows to 62.92 km² in winter but shrinks to 35 km² in summer, which makes Hourtin-Carcans the largest freshwater lake entirely within France.