Saint-Brieuc is named after a Welsh monk Brioc, who Christianised the region in the 5th century and established an oratory there. Bro Sant-Brieg/Pays de Saint-Brieuc, one of the nine traditional bishoprics of Brittany which were used as administrative areas before the French Revolution, was named after Saint-Brieuc. It also dates from the Middle Ages when the "pays de Saint Brieuc," or Penteur, was established by Duke Arthur II of Brittany as one of his eight "battles" or administrative regions.