Horror Vacui () is a 1984 German avant-garde film directed by Rosa von Praunheim.
The film was shown at international film festivals and in 1985 at the Museum of Modern Art in New York City.
Shot in a neo-expressionist style, the film is a satire on cults of any kind. The plot follows Frankie and Hannes, a young gay couple living in Berlin. One is studying art and the other medicine. Their happy life is disrupted when Frankie attends a lecture and quickly becomes involved in a sinister cult operating as a self-help group called "Optimal Optimism". 'Madame C', a former Nazi party member, is the leader of 'Optimal Optimism'. When the cult members find out that Frankie is gay, they rape him. Hannes has to find a way to save him.
"If you have a soft spot for fantastic and ironic films, you won't feel any inner emptiness [horror vacui] with Praunheim's wealth of fantasy." (Cinema Film Journal)