Château de Suscinio is a medieval castle located in the commune of Sarzeau, in the French department of Morbihan, in the region of Brittany. The castle was originally built in the 13th century as a hunting lodge for the Dukes of Brittany and was later expanded and fortified in the 14th and 15th centuries.

Château de Suscinio was an important residence for the Dukes of Brittany until the 16th century, when the duchy was annexed to the French Crown. The castle was later used as a prison, a refuge for the persecuted, and a farm. It was classified as a historical monument in 1840 and is now open to the public as a museum.

The castle is surrounded by a moat and has two main parts: the keep and the residential buildings. The keep is a massive tower with a height of 30 meters and a diameter of 13 meters. It has six floors, including a dungeon and a chapel. The residential buildings consist of several wings built around a courtyard, including a great hall, a chapel, and the apartments of the duke and his family.