The Château de Combourg is a castle in the commune of Combourg in the Ille-et-Vilaine département, in Brittany, France.
The castle stands on a small hill next to Lac Tranquille (Lake Tranquil) in the town. The original castle on the site was built around 1025 by Archbishop Guinguené, who gave it to his illegitimate brother Riwallon. Major alterations were made between the 15th and 19th centuries.
The castle consists of four large, powerful buildings of dressed granite, with crenellations and machicolations, enclosing a rectangular courtyard. In each corner of this massive fortress is a round tower, also with crenellations and machicolations, with conical roofs.
In 1761, the Chateaubriand family acquired the property and it was the childhood home of François-René de Chateaubriand (1768–1848).
Privately-owned, the Château de Combourg is listed as a monument historique by the French Ministry of Culture. This building is open to the public.