Rhythmus 21 is a 1921 German absolute film directed by Hans Richter. Rhythmus 21 was made in black and white, and spans for approximately 3 minutes. The film is the first installment of Richter's Film Ist Rhythm series and is considered, by experts, an early and influential film to the abstract film movement. Many absolute films were described as a mixture of art, film, and music because they present on the screen many musical elements such as dynamics, rhythm, and motion. The films in this series get their name from their visual rhythmic element that closely resembles music.