Geoffrey of Monmouth, c.1100-1154, English author. He was probably born at Monmouth and was of either Breton or Welsh descent. In 1152 he was named bishop of St. Asaph in Wales. His Historia regum Britanniae (written c.1135), supposedly a chronicle of the kings of Britain, is one of the chief sources of the Arthurian legend. Geoffrey was the first to write a coherent account of Arthur, establishing the great warrior as a national hero, the conqueror of Western Europe. He drew information from the writings of Bede, Gildas, Nennius, the Welsh chronicles, and folklore, and imaginatively wove the whole into a fictional narrative in the form of a history. His work had great influence on Wace, Layamon, and many chroniclers of the Middle Ages. Another work attributed to him, the Vita Merlini (1148), also influenced later stories of Arthur and Merlin.

(died 1155) Medieval British chronicler. He was probably an Oxford cleric for most of his life. His mostly fictional History of the Kings of Britain (circa 1135–39) traced the descent of British princes from the Trojans; it brought the figure of Arthur (see Arthurian legend) into European literature and introduced the enchanter Merlin, whose story Geoffrey related in the Vita Merlini (circa 1148–51?). Though denounced from the first by other historians, the History was one of the most popular books of the Middle Ages and had an enormous influence on later chroniclers.

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