Saint-Brieuc (săN-brēöˈ) [key], town (1990 pop. 47,370), capital of Côtes-d'Armor dept., NW France, on the Gouet River near its mouth on the Bay of Saint-Brieuc, an arm of the English Channel. Tourism, metallurgy, and textiles are the chief industries. Saint-Brieuc was probably founded in the 5th cent. and grew rapidly after St. Briomach, the Welsh missionary for whom the town was named, built a monastery there (6th or 7th cent.). An episcopal see since the 9th cent., the town was the meeting place for the provincial estates of Brittany in the 17th and 18th cent. Many old houses remain, and there is a Gothic cathedral.