In 1897, Henri d'Orléans, Duke of Aumale and son of Louis-Philippe I, bequeathed the Chateau and its collections to the Institut de France. It included both rooms remodeled as museum spaces and those left as residential quarters in the styles of the 18th and 19th centuries.
The collection of old master paintings is among the most important in France. It consists predominantly of Italian and French works and includes three paintings by Fra Angelico, three by Rafael, five by Nicolas Poussin, four by Antoine Watteau and five signed by Ingres.
The museum harbors a collection of 2,500 drawings and a library including 1,500 manuscripts, of which 200 are illuminated. The most renowned of the latter are the Très Riches Heures du Duc de Berry. In addition to these, there are collections of prints, portrait miniatures, sculptures, antiques, old photographs, decorative arts, furniture and porcelain.
The collection may only be seen at Chantilly due to the conditions attached to the bequest by the Duke d'Aumale. These conditions forbid the loaning of artworks to other institutions as well as insisting that the exhibition spaces not be modified in any way. As a result, the museum remains almost unchanged since it was opened in 1898.