Vieille Cour Castle, Medieval castle in Oudon, France.

Vieille Cour Castle is a ruined medieval fortress on a slope above the Hâvre valley, north of Oudon. Its surviving lord's hall has a southern gable wall 14 metres high, with a brick chimney flue, putlog holes, two windows, two corbels, two large bays and three doors. The high court keeps a leaning defensive tower 8 metres tall, a double gatehouse and over 200 metres of curtain wall.

Vieille Cour is first mentioned in 1140, when Geoffroy d'Oudon, mortally wounded at Champtoceaux, gave the monks of Oudon his meadows "de Veteri Curte". After the first castle of Oudon was destroyed in the early 13th century, the lords of Oudon built anew here; Amice, daughter of Geoffroy de Beaumortier, married Galeran III de Châteaugiron, and the residence was erected in the second half of the 13th century by the Châteaugiron family. The castle was dismantled from 1392 onward.

The ruins display medieval defensive design through visible walls and a gatehouse that reveal how the site once protected the surrounding lands. The elevated position shows how carefully the location was chosen to control the valley below.

The ruins are private property, listed as a site by decree of 26 November 1942, and no public visiting arrangements are documented. The site lies north of Oudon's village near La Mabonnière, above the Hâvre valley, and the lower court is now a chestnut grove crossed by a path leading up to the castle. The ground is uneven and the moats reach 2 to 3 metres deep on the north-west side.

The great hall of the lord's residence measures 20 by 13 metres, and the historian Nicolas Faucherre calls it the only surviving example of a large seigneurial hall with its timber frame in the Nantes region. The ruined building keeps a 14-metre south gable, a brick chimney flue, putlog holes, two windows, two corbels, two large bays and three doors.