The Chateau d'Armainvilliers is a historic château that today extends over the municipalities of Tournan-en-Brie and Gretz-Armainvilliers in Seine-et-Marne, France, approximately 30 miles east of Paris.

Under the Restoration, the château was returned to Louise Marie Adélaïde de Bourbon, Duchess of Orléans, the wealthiest heiress in France prior to the French Revolution following the death of her brother, Louis Alexandre, Prince of Lamballe, in 1768 (the only two surviving children of the Duke of Penthièvre).

[7] In 1863, the Duchess brought a lawsuit against her neighbor Émile Péreire,[8] "on the ground that he had infringed her rights by giving the name of Château d'Armainvilliers to a mansion which he has built in the vicinity of her residence.

His son, King Mohammed VI, sold the château for €200 million in 2008, reportedly to Esam Janahi, a leading figure in Islamic finance.

[13] In 2024, the 100-room 96,875 sq ft (9,000.0 m2) château situated on nearly 2,500 acres was listed for sale for €425 million,[14] which if sold at that price, would be the most expensive house in the world.