 The abbey was founded as a Benedictine monastery of nuns in the late 11th century by William the Conqueror and his wife Matilda of Flanders as the "Abbaye aux Dames" ("Women's Abbey"), as well as the "Abbaye aux Hommes" ("Men's Abbey"), formally the Abbey of Saint-Étienne.The works began in 1062, starting from the rear and finished in 1130.Matilda, who died in 1083, was buried in the choir under a slab of black marble.