Aucassin is a medieval French narrative poem, part of the Aucassin et Nicolette story, which combines elements of romance and adventure. It is notable for its unique structure, alternating between prose and verse, and tells the tale of a young nobleman, Aucassin, who is in love with Nicolette, a beautiful girl of uncertain origin. Their love faces numerous challenges, including family opposition and societal norms. The poem is set in the Provence region and reflects themes of love, loyalty, and the struggle against societal constraints. It is one of the few surviving examples of medieval literature that showcases the blending of different literary forms, making it an important work in the study of Old French literature.