Castelnaud  -   or rather, Castelnau, meaning the “new castle”  -   was certainly founded in the 12th century.   At the beginning of the 13th c., its lordly owner was
Bernard de Casnac, a supporter of the Cathars (also known as the Albigensians), whose dualist religious beliefs led to them being castigated as “heretics”.   In 1214, the castle was seized by Simon de Montfort, a northern baron who had been sent down to crush the Cathar “heresy”.  Subsequently, the fortress was rebuilt.  Its keep and the courtine, or “curtain (the area between two bastions), date from this period.

During the Hundred Years War, the château was often in English hands.  The French finally took it in 1442, after a siege ordered by France’s King Charles VII.   Once hostilities ended, it was restored to the Caumont family, who had owned it since 1368.  They strengthened its defensive capabilities:   gun ports were installed in the lower wall and the new barbican, and the artillery tower was erected.
A large new main building was also erected, to try to make the medieval fortress more comfortable.   Nevertheless, the Caumonts quit Castelnaud to live in their pleasanter new château at Milandes.

During France’s bitter Wars of Religion (1562-98), the castle was left in the hands of
Captain Geoffroy de Vivans, a Protestant soldier nicknamed “The Battler”, who was born at Castelnaud.  He was so feared that it was never attacked in all that time.

In the 17th century, the château was rarely inhabited.  Abandoned after the French Revolution (1789), it fell more and more into disrepair and, in the 19th century, even served as a stone quarry.

In 1966, it was listed officially as an Historic Site and has since been brought back to life through a series of outstanding restoration programmes.  Its “Museum of Medieval Warfare” was founded in1985.

See also the account of Castelnaud's historic personalities