Geoffrey of Monmouth was a 12th-century cleric and historian from Wales, best known for his work "Historia Regum Britanniae" (The History of the Kings of Britain). This influential text, written around 1136, chronicles the history of Britain from its legendary origins to the Anglo-Saxon period, blending history with myth. Geoffrey's writings introduced many famous figures, including King Arthur and Merlin, to a wider audience, shaping the perception of British history and folklore. His work laid the foundation for later medieval literature and inspired numerous adaptations in various art forms, including literature and film.