Monk at Jumièges Abbey in France in 664. Spiritual student of Saint Philibert. Spent several years travelling from monastery to monastery. Companion to Saint Ouen of Rouen in Rome, Italy for more than ten years. Sent by Ouen to found a monastery near the city of Rouen; it was known as Saint-Saëns, France and was destroyed in the 9th century by war. Sidonius founded several other monasteries in this region, and served as abbot, before retiring to live as a simple monk. Spiritual teacher of Saint Leutfridus.
- c.690 of natural causes