The Matter of Britain (French: matière de Bretagne) is the body of medieval literature and legendary material associated with Great Britain and Brittany and the legendary kings and heroes associated with it, particularly King Arthur. The 12th-century Welsh cleric Geoffrey of Monmouth's Historia Regum Britanniae (History of the Kings of Britain), widely popular in its day, is a central component of the Matter of Britain. It was one of the three great Western story cycles recalled repeatedly in medieval literature, together with the Matter of France, which concerned the legends of Charlemagne, and the Matter of Rome, which included material derived from or inspired by classical mythology and classical history. Its pseudo-chronicle and chivalric romance works, written both in prose and verse, flourished from the 12th to the 16th century. Source: Wikipedia (en)