Phare de Tréhiguier, lighthouse in Morbihan, France

Phare de Tréhiguier is a lighthouse in the village of Tréhiguier, Pénestin, on the left bank of the Vilaine. Its square tower, 13 m high, rises from the ridge of a low building; it is white masonry with raised corner quoins, four small windows stacked on the front face, a small balcony near the top and a steep pyramidal roof of slate. Since 1995 it has housed the Maison de la mytiliculture.

Built in 1881 and lit the following year, the lighthouse worked in alignment with the Phare du Scal to guide ships through the Vilaine estuary; it was sometimes called the "rear light". Allied bombing damaged it in December 1944, and it resumed service in 1947. It was automated in 1971, but the Arzal dam slowed river navigation, and the light was permanently extinguished in 1989. The commune of Pénestin bought it in 1990 and restored it.

Since 1995 the former lighthouse has housed Pénestin's Maison de la mytiliculture, devoted to mussel farming on the Vilaine estuary. The building is sometimes called the "rear light", the Scal lighthouse being the "front light". The museum occupies a lighthouse deactivated in 1989, so the setting itself is part of what is shown.

The lighthouse stands in the village of Tréhiguier, on the left bank of the Vilaine in Pénestin. The tower is 13 m high with a square section, and the former lamp was on the fifth floor. The Maison de la mytiliculture, installed by the commune in 1995, occupies the building.

The tower is 13 m high with a square cross-section, not cylindrical, and its lamp of 6,000 W sat on the fifth floor. It worked in tandem with the Phare du Scal: Tréhiguier was the "rear light", Scal the "front light", aligned to guide ships into the Vilaine estuary.