Château Castagnac is an estate in the commune of Saint-Aignan in the Fronsadais on the right bank of the Bordeaux region. It produces red wines under the Fronsac AOC.

Owner: Bernard Coudert.

Vineyards: 7ha of which 1.3ha of Fronsac and and 5.7ha of Bordeaux AOC taken en fermage by Bernard Coudert in 1990 from the daughter of his aunt.