The material of Brittany is the name given to all the texts written in the Middle Ages around Breton legends, in particular those of the Arthurian cycle. It represents the Celtic tradition, as opposed to the Carolingian tradition of matter from France and the Latin and ancient traditions of matter from Rome.
The poet Jean Bodel (1165-1210) wrote that there were three materials:"Those of France, Brittany and Rome. These three materials are not alike. The tales of Brittany are so unreal and seductive! While those of Rome are learned and charged with meaning and that those of France see their authenticity confirmed every day!"
The matter of Brittany does not present the unity of composition which characterizes the Iliad or the Odyssey for example. There is not an Arthurian legend, but Arthurian legends, among others. This is due to the many authors who have assembled these traditions over the centuries, from the first collecting monks to the writers who have enriched it, such as Chrétien de Troyes or more recently Xavier de Langlais. Thus the names of the characters and the circumstances of their lives (youth, great deeds, death) vary from one era to another, from one country to another. There is, however, a unity of place:the mythical kingdom of Brittany (England, Wales and mainland Brittany), and an approximation of the time:the 6th century, i.e. after the fall of the Western Roman Empire, in the time of the great invasions. They are therefore not medieval characters, even if their popularity in France was carried by writers from the Middle Ages.