Het Kasteel van Mortefontaine (Frans: Castle of Mortefontaine) is een kasteel in de Franse gemeente Mortefontaine. Het kasteel is een beschermd historisch monument sinds 2004.
Het kasteel is echter niet direct te bezoeken.
The Chateau de Mortefontaine is a 17th century French chateau located in Mortefontaine, in the Oise department and the Hauts-de-France region. Built during the period between 1600 and 1630 for the lord of Plailly-Montmélian, Philippe Hotman, it became the power center of the Marquisate of Plailly-Montmélian, erected in 1654, whose administrative headquarters remained in Plailly. The castle is best known for having been the country residence of Joseph Bonaparte from 1798 to 1814, which makes it a high place of social life. Today it is a private residence, which has lost its splendor after having served as a school between 1949 and 1958, then as a luxury hotel from 1987. Of the English-style park designed in 1770, nothing remains significant on this part of the domain.
In the central Middle Ages, the châtellenie of Montmélian, on which Mortefontaine depends, belonged to the crown, until King Philippe-Auguste gave it in exchange for the seigniory of Vernon to Richard de Vernon and his son Richard. A large part of the land belongs to the Bouteiller de Senlis family. Richard II of Vernon has no male descendants. His daughter Marie married the knight Guillaume Calletot, who decided to give all his possessions in the country of France to the abbey of Saint-Denis in 1283. Mortefontaine therefore had two lords, the abbey of Saint-Denis represented by a provost called procurator. and lord, and Jean le Bouteiller, lord of Chantilly. In 1345, Guillaume IV le Bouteiller, heavily in debt, gave up the entire Montmélian domain to his brother-in-law Robert de Clermont, and only kept the "square tower" as a residence.