Abbaye de Lonlay, Gothic abbey and monument historique in Lonlay-l'Abbaye, France.

Abbaye de Lonlay is a monastery featuring a three-level Gothic choir surrounded by an ambulatory and multiple chapels. The stonework displays Romanesque techniques visible in the limestone capitals throughout the structure.

Founded around 1020 by Guillaume I of Bellême as a Benedictine monastery, it was populated with monks from Fleury Abbey. This establishment made it an important religious center in the region.

The abbey's name survives in the village toponym Lonlay-l'Abbaye, and the foundation charter of Guillaume I of Bellême is the key document of its early history. The charter was confirmed at Tinchebray between 1150 and 1190 by Henry II of England, Duke of Normandy, again by Pope Gregory X in 1271, and by Henry IV of England at Rouen in 1423 during the Hundred Years' War. The monastic cartulary was lost, which is why the list of abbots is hard to reconstruct.

The site is accessible to visitors and offers guided tours as well as learning programs for school groups. This allows interested guests to study medieval religious architecture firsthand at the location.

The abbey exercised authority over eight priories including Saint-Symphorien in Domfront and Saint-Gilles de la Place in Sarthe. This network of affiliated monasteries extended its religious influence across a large territory.