Ludwig Achim (or Joachim) von Arnim (January 26, 1781 – January 21, 1831), German poet and novelist, was born at Berlin.

He studied natural science at Halle and his bent was from the first towards literature. From the earlier writings of Goethe and Herder he learned to appreciate the beauties of German traditional legends and folk-songs; and, forming a collection of these, published the result (1806-), in collaboration with Clemens Brentano under the title Des Knaben Wunderhorn. Brentano's sister Bettina became his wife and won wide recognition as a writer in her own right.