Lucius Tiberius (sometimes Lucius Hiberius, or just simply Lucius; also Thereus in Claris et Laris) is a Western Roman procurator or emperor from Arthurian legend, who is killed in a war against King Arthur. First appearing in Geoffrey of Monmouth's Historia Regum Britanniae, Lucius also appears in later, particularly English literature such as the Alliterative Morte Arthure and Thomas Malory's Le Morte d'Arthur. The motif of a Roman Emperor defeated by Arthur appears in the Old French literature as well, notably in the Vulgate Cycle.