Valmont Abbey (Abbaye de Valmont, Sainte-Marie de Valmont or abbaye Sainte-Marie) was a Benedictine abbey in Valmont, Seine-Maritime, France. Its chapel and surviving ruins of other parts of the abbey were classed as a historic monument in 1951 and the facades and rooves of all the abbey buildings were made historic monuments in 1965.
It was founded in 1169 by Nicolas d'Estouteville with Benedictines split off from Hambye Abbey. It never held more than 25 monks and was destroyed and rebuilt several times, with the abbey church only truly completed in the 16th century - countess Marie II of Saint-Pol is buried in it.
The abbey buildings were built from 1678 to 1782 under Louis de La Fayette (1634–1729), commendatory abbot, who tried to introduce the Saint Maur reforms to the abbey. It was finally reformed in 1754 by the Maurists and was rebuilt during the second half of the 18th century, until the French Revolution, when it was dissolved - its monks were dispersed in 1789 and its buildings sold off to private owners in 1791.
The painter Eugène Delacroix often holidayed at the Valmont manor house and the abbey ruins inspired his drawing Ruines de l'abbaye de Valmont, now in the musée du Louvre. The abbey became a monastic site again in 1994, re-founded by Benedictines from Notre-Dame-du-Pré at Lisieux and re-dedicated in 2004.