Lac de Lourdes, Glacial lake in Hautes-Pyrénées, France.

Lac de Lourdes is a glacial lake in the Hautes-Pyrénées, formed behind a moraine of the Argelès glacier. It covers about 52 hectares at 422 metres, with a maximum depth of 12 metres. Its western part has become marshland, reducing the original surface by about a quarter. The south shore borders the disused Lourdes golf course, and the north bank lies in the neighbouring commune of Poueyferré.

The area was acquired in the 1700s by the Prince of Rohan-Rochefort, who planned to drain it for farmland. The French Revolution stopped this project and the water remained.

Local legend long treated the lake as cursed: the soul of anyone who drowned was said to stay trapped at the bottom. Another tale holds that a cruel city once stood here, sunk by God, with only a pious family warned to flee without looking back; the wife turned and was changed to stone.

Access from Tarbes is by turning right at the entrance to Lourdes, before passing under the railway line. The lake lies in the Bois de Mourles–Forêt de Béout district; its northern bank belongs to the neighbouring commune of Poueyferré. The western part has become marshland, so the water covers about a quarter less than its former extent.

Next to the lake sits a peat bog protected as a Natura 2000 site since 2006, home to rare plants like sundew and butterflies including the false ringlet. This protected area makes the location valuable for nature watchers.