Abbaye Sainte-Croix de Guingamp, Abbey ruins in Guingamp, Côtes-d'Armor, France

Abbaye Sainte-Croix de Guingamp is a ruined abbey in Guingamp, Brittany. Its surviving church walls date mainly from 1748–1750, when only the polygonal chevet and the crossing of the transept were saved. The crossing is the last remnant of the late 12th- or 13th-century building, with four broken triple-roll arches on columns whose capitals are carved with water leaves and crockets. The 16th-century abbatial house has a hexagonal stair turret with a circular top.

Founded in 1134 by Count Étienne I of Penthièvre and his wife Havoise de Blois for Augustinian canons from Saint-Victor in Paris, the abbey was partly rebuilt by Abbot Jean Hamon (1437-1452) with support from Count Pierre de Guingamp, then by Abbot Jean de Kernavanay (1514-1536). Around 1750 only the transept crossing and polygonal chevet could be saved; during the Revolution the abbey was sold as national property and gradually disappeared.

The abbey's name comes from the Holy Cross, and its canons followed the Rule of Saint Augustine, from the Parisian abbey of Saint-Victor. A local legend survives in the story of Henri de Penthièvre, who expelled Abbot Moyse and installed his mistress as "abbess" before repenting and marrying her. The abbey was spared plunder during the Wars of the League, the only monastery in Guingamp to escape it.

The site is accessible during the day for self-guided exploration of the ruins and surrounding grounds. Wear comfortable walking shoes as the terrain is uneven and pathways wind between the stone structures.

The pedestrian entrance arch of the 18th century carries a stone plaque engraved with the safeguard granted to the abbey by Louis XIII in 1636, not the 18th century. The abbey was the only monastery in Guingamp spared when royal troops pillaged the town during the Wars of the League.