The Château de Castelnau-Bretenoux (French pronunciation: [ʃato də kastɛlno bʁətnu]) is a castle in the commune of Prudhomat, Lot département, France. One of the most impressive in the Quercy region, it has been listed as a monument historique by the French Ministry of Culture since 1862.

Construction began about 1100, under Hugues, baron of Castelnau, who built a wall around his manor. He was the ancestor of the powerful dynasty of Castelnau, who owned a rich and prosperous region and were vassals of the Counts of Toulouse.

The castle was enlarged several times between the 12th and the 15th century, when it was necessary to adapt the fortifications to artillery.

It was taken by Henry II of England in 1159, and returned to the barons of Castelnau at the end of the Hundred Years' War.

During the 17th century, the castle was improved in an aesthetical and practical way: large windows, richly decorated salons, balcony of honor.

The castle fell into disrepair after the death in 1715 of the last Castelnau, the twelve year old daughter of Louis-Guillaume, he had died in 1705, and it reverted to his widow, a member of the de Luynes family.

The French Revolution occurred in 1789 but it was years later on 26 December 1793, a decree had been issued, calling for the destruction of the castle's towers, battlements, drawbridge, and the emptying of the moat. The decree was ignored except for the moat being emptied and the drawbridge permanently lowered. The library and archives were however destroyed in a bonfire. No maintenance occurred and it was neglected for thirty years.

In 1830, the de Luynes family descendants sold the castle. A man called Lacoste purchased it, with the idea of restoring it but instead sold it to a Mr. Molin de Teyssieu, who in turn thought about demolishing it. The French people and government would not allow that to happen. However, no restoration work or government buy-back occurred.

On 28/29 January 1851, when a fire broke out in the castle, the large gallery and buildings in the courtyard were destroyed. The insurance company bought it and sold it to a Mr. Dubousquet with an idea to convert it into a monastery. The idea failed and it was bought by Father Selve in 1873. On the death of the priest in 1880, a man named de Pradelle purchased it and began selling its stone.

Finally in 1896, its last private owner, Jean Mouliérat purchased the castle and spent thirty years restoring the building and rooms interiors. He was a singer with the Paris Opéra Comique and a collector of furniture and sacred artworks. Between 8 and 18 April 1932, Moulierat donated the castle to the French state, dying on 20 April 1932. Visitors can see seven rooms in this fortress, restored and furnished in the medieval style.

The castle of Castelnau-Brenenoux is located on the top of a hill, at the intersection of several valleys; among them is the river Dordogne. The castle is visible from a distance and easily recognizable by its walls of red stone.

The layout is nearly a triangle, with round towers at each angle. The square keep and the main building of the medieval period still remain. Its conception was very imposing, with three enclosing walls, wide curtain walls, and nine round towers.

A small village has surrounded the castle, along the slopes of the hill.

• List of castles in France

• Château de Castelnau-Bretenoux - official site
• Base Mérimée: Château de Castelnau-de-Bretenoux, Ministère français de la Culture. (in French)
• Aerial picture

44°53′57″N 1°49′35″E / 44.8992°N 1.8264°E / 44.8992; 1.8264