Château d'Auray, Medieval castle ruins in Auray, France.

Château d'Auray is a castle ruin in Auray's historic center, with visible remains including a round tower and supporting walls that overlook the river and harbor. The site occupies a position along the waterfront that once formed a key part of medieval town defenses.

The castle was built in 1096 to protect a river crossing and rebuilt in 1201 under Arthur I of Brittany to strengthen its defenses. The site gradually lost its military function and was eventually left in ruins.

The name survives in Rue du Château, laid out on 6 September 1560 over the filled northern moat; within years it was lined with houses, some timber-framed, others in limestone favoured in the 17th and 18th centuries. In 1635 the town gave the western moat and the castle site to nuns wanting to settle in Auray, for their garden, plus 3,000 livres.

The ruins are located in the old town and can be reached via Rue du Château, which was constructed over the former northern moat. The site is easily accessible on foot and free to visit.

Henry II ordered the ruin demolished, but his prosecutor required that the wall on the river side be kept; it still stands on the right bank of the Loc'h. The king gave the castle stones in 1558 to the monks of Sainte-Croix de Quimperlé, owners of Belle-Île, to build the fort of Le Palais against English pirates; the rest was auctioned in 1559.