Chateau Léhon, Medieval fortress in Léhon, France.

Château Léhon is a medieval fortress perched on a rocky promontory above the Rance valley, with trapezoidal walls and semicircular towers built during the 13th century. The structure displays multiple building phases spanning from the medieval period, each visible through variations in stonework and defensive design throughout the ruins.

The fortress was first documented in 1034 as a strategic defense point shaped by regional conflicts in Brittany. It underwent multiple destructions and rebuildings over centuries, which explains its current fragmentary appearance.

The name Léhon comes from the Breton Kastell Lehon, and the fortress was the seat of ducal power for the Dinan region after Duke John I the Red bought it in 1264. In 1664 Louis XIII gave the ruins to the abbot Charles Bruslard so the monks of Léhon Abbey could take stone for their buildings. The governors of Dinan kept the title "Governor of the castles of Dinan and Léhon" until the French Revolution.

The site is freely accessible daily, with parking available nearby at Allée du Château or at the Léhon tennis club. The ruins sit on uneven ground with steep pathways, so sturdy shoes and careful footing are recommended.

The chapel of Saint Joseph was built in 1875, not on the dungeon, but on the castle ruins donated to the parish in 1872 by the heirs of Reslou de Guemen; it was demolished in 1964, leaving only a statue of Saint Joseph. The heirs had asked that a chapel be erected on the ruins.