The Château de Lacoste or La Coste is a ruined castle in the commune of Lacoste in the Vaucluse département of France.
The castle is sited on an extension of the northern flank of the Little Luberon on which the village stands. This position offers its occupants superb views over the valley of the Calavon, the Monts de Vaucluse, Mont Ventoux and the Alps, as well as the village of Bonnieux which can be seen on a neighbouring hill.
The castle's origins are in the 11th century, but it was largely modified in subsequent centuries.
It was for many years the property of the Simiane family.
Two hypotheses are suggested for the transfer of the castle from the Simianes to the Sades.
The Marquis de Sade stayed there from 1769 to 1772, between the scandals at Arcueil and Marseille, then after the latter and his flight to Italy, he took refuge there until his incarceration in the Château de Vincennes in 1777. Escaping while being transferred to Aix, he took refuge there for the last time from 16 July to 7 September 1778 before being returned to Vincennes.
It was in 1772 that he made his longest stay there, during which he built in the castle a theatre capable of holding 120 spectators. Throughout his internments, he maintained an extraordinary attachment (un attachement extraordinaire) for La Coste.
During the French Revolution, the castle was vandalised and largely destroyed. The construction materials were sold.
Crippled with debts, in year IV of the Republic (1796) the castle and its estate were sold to Rovère, deputy of Vaucluse and a native of Bonnieux, who, a victim of the Coup of 18 Fructidor, was deported to French Guiana where he died at Sinnamary in 1798.