Castle in Mont-Saint-Jean, Medieval fortress in Mont-Saint-Jean, France.

The castle at Mont-Saint-Jean is a medieval fortress built with a rectangular keep and four corner towers linked by curtain walls. It sits elevated above the Serein River valley and remains a private residence today.

A fortified mound stood here before the year 1000; in 924 Raoul, Duke of Burgundy and King of France, besieged Mont-Saint-Jean. In 1305 Etienne, lord of Mont-Saint-Jean, acknowledged his castle as "jurable et rendable" to the duke, and in 1358 Hugues de Mont-Saint-Jean exchanged it with Girard de Montbelet for the lordship of Montbelet. By 1658 it was a fortress of ten large towers linked by a strong wall.

The castle's Romanesque church stands within the southern enclosure, flanked by two round towers to the east and a square tower to the south. The castle entrance was once on the north side via a drawbridge facing the village, but today access is from the west through an open-air corridor. The chapel occupies the first two levels of the western building, to the right of the gate tower.

The castle stands on a spur south of the village, about 100 metres above the north bank of the Serein and the east bank of the RD 117. The entrance to the enclosure was once on the north via a drawbridge facing the village; today access is from the west through an open-air corridor. The site is classified as a historical monument, with the walls and towers separately inscribed.

The castle's keep had four corner towers and a drawbridge, with a cistern and a deep well inside. The north-west tower was fitted with latrines, and the south-east tower holds a staircase down to a postern giving access to the moats. The north-east tower projects further than the others and is reached through an opening at the centre of its vault.