Le Cosquer tide mill, Tide mill in Troguéry, France.

Le Cosquer is a tide mill located in Troguéry where the Jaudy river meets tidal waters. The building retains original equipment that millers once used to grind grain by capturing the energy of changing water levels.

A water mill on the right bank of the Jaudy belonged to the seigneurie of Troguéry by 1601, when it was already in ruins. The tide mill known as Bili-Gwenn was entirely rebuilt in 1840, and a grain and flour store was added in 1841. It was classified as a monument historique on 20 December 1999, with the mill, its machines, the store, the dike and the retaining wall protected.

The structure reflects how coastal communities in Brittany developed practical solutions to harness natural forces for daily work. It shows the skills and knowledge passed down through generations of millers who worked with the tides.

The mill stands on the right bank of the Jaudy in Troguéry, Côtes-d'Armor. The protected elements are the mill with all its machinery, the grain store, the dike with its loading quay and the retaining wall on the east side of the pond; the south-east return wing is excluded. The building is not open as a visitable museum, so the structures are seen from outside.

In 1903 it became the first mill of its kind to replace the water wheel with a hydraulic turbine; a diesel engine followed in 1932 and electrification in 1938, yet the mill kept the sea's reflux as auxiliary power. Milling continued as Minoterie Thomas until 1991.