Château de Marsac, Medieval castle in Marsac, France.

Château de Marsac stands on a hill in the village of Marsac, Tarn-et-Garonne, near the Gers border. Its oldest element is a square tower from the 12th–13th centuries, the oldest in the department. The ground floor has a barrel-vaulted room linked to the upper floor by a trapdoor in the vault. The Renaissance facade dates from around 1557, with later windows and a 19th-century balcony.

Marsac was originally the seat of a lordship held by Sans Garcié de Manas, then by the Montesquiou, English barons, in 1277. Jean de Montesquiou became sole lord in 1641; the estate passed to Jean-Paul de Rochechouart in 1677, then in 1741 to Melchior François de Reversat de Céles, a counsellor at the Toulouse Parlement, through his wife Marie Thérèse d'Auterive. The castle was largely remodelled in the Renaissance, with staircase and windows dated to 1557.

The castle displays Renaissance facades from 1557 that show how the medieval fortress was transformed into a noble residence. This transformation reflects how the tastes and lifestyles of its inhabitants changed over time.

The château is private property and cannot be visited; its façades and roofs are protected as monuments historiques, and the whole building is classified. It stands on a hill in the centre of Marsac, in Tarn-et-Garonne near the Gers border, so it is seen from the village streets and surrounding paths. The former stables and outbuildings that once closed the courtyard were demolished in the early 19th century, opening the view over the village.

The square tower is the oldest in Tarn-et-Garonne, dating from the 12th–13th centuries. Its ground-floor barrel-vaulted room is reached from above through a trapdoor set into the vault, a defensive arrangement probably built in the 13th or 14th century. The castle is private and cannot be visited.