Die dunkle Seite des Mondes () is a novel by the Swiss writer Martin Suter, first published by Diogenes Verlag in 2000. It is about a successful business lawyer who has a midlife crisis, starts an affair with a younger bohemian woman, takes hallucinogenic mushrooms and has a personality change that makes him violent and dangerous. The title is a reference to the album The Dark Side of the Moon by Pink Floyd.
The book was adapted into the 2015 film ' directed by and starring Moritz Bleibtreu.