The Matter of Britain 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. It was one of the three great 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.

The Matter of France, also known as the Carolingian cycle, is a body of literature and legendary material associated with the history of France, in particular involving Charlemagne and his associates. The cycle springs from the Old French chansons de geste, and was later adapted into a variety of art forms, including Renaissance epics and operas. Together with the Matter of Britain, which concerned King Arthur, and the Matter of Rome, comprising material derived from and inspired by classical mythology, it was one of the great literary cycles that figured repeatedly in medieval literature.

According to the medieval poet Jean Bodel, the Matter of Rome was the literary cycle made up of Greek and Roman mythology, together with episodes from the history of classical antiquity, focusing on military heroes like Alexander the Great and Julius Caesar. Bodel divided all the literary cycles he knew best into the Matter of Britain, the Matter of France and the Matter of Rome (although "non-cyclical" romance also existed).[1] The Matter of Rome also included what is referred to as the Matter of Troy, consisting of romances and other texts based on the Trojan War and its after-effects, including the adventures of Aeneas.[2]