The Old Mellifont Abbey are ruins of a Cistercian Abbey near Drogheda, County Louth in Ireland.

Founded in 1142 by the order of Archbishop of Armagh, Saint Malachy, the abbey had in 1170 about a hundred monks and three hundreds lay brothers and became a model for anothers Cistercian abbeys in Ireland. It was the most important abbey until it was closed in 1539 to transform in a fotified house.