Fontenelle Abbey or the Abbey of St Wandrille is a Benedictine monastery in the commune of Saint-Wandrille-Rançon, founded in 649 near Caudebec-en-Caux in Seine-Maritime, Normandy, France.
It was founded by Wandregisel or Saint Wandrille (died 668) on land obtained through the influence of Wandregisel's friend Saint Ouen, Archbishop of Rouen. Wandrille held a high position at the court of his king, Dagobert I, but wishing to devote his life to God, he retired to the abbey of Montfaucon-d'Argonne, in Champagne, in 629. Later he went to Bobbio Abbey and then to Romainmôtier Abbey, where he remained for ten years. In 648 he returned to Normandy and established the monastery of Fontenelle, using the Rule of Saint Columbanus, which he had known at Bobbio; the deed of gift of the land is dated 1 March 649.
He first built a Carolingian style basilica dedicated to Saint Peter, nearly 300 feet (91 m) long, which was consecrated by Saint Ouen in 657. (This church was destroyed by fire in 756 and rebuilt by Abbot Ansegisus (823–33), who added a narthex and tower).
The monastery was extremely successful at first, and produced many saints and prelates. In 740 however there began a series of lay abbots, under whom the monastery declined. Ansegisus, the reformer of Luxeuil Abbey, was appointed in 823 abbot of Fontenelle, which he also reformed.