(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 (c. 1135–39) traced the descent of British princes from the Trojans; it brought the figure of Arthur (seeArthurian legend) into European literature and introduced the enchanter Merlin, whose story Geoffrey related in the Vita Merlini (c. 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.