Achim von Arnim was a German poet, novelist, and playwright of the early 19th century, known for his pivotal role in the German Romantic movement. He is most celebrated for his contributions to folk poetry and his collaboration with Clemens Brentano, which aimed to revive interest in traditional German folklore and ballads. Arnim's work emphasized themes of nature, emotion, and the supernatural, reflecting the broader ideals of Romanticism.