 Coriallo housed a small garrison and a castrum was built on the left bank of the Divette as an element of the "Litus saxonicum", after Saxon raids at the beginning of the 4th century.In 497, the village was sold with all of Armorica to Clovis.It was evangelised by in 432, then by Saint Exuperat, Saint Leonicien, and finally Saint Scubilion in 555.