Peter Ulrich Weiss (8 November 1916 – 10 May 1982) was a German writer, painter, graphic artist, and experimental filmmaker of adopted Swedish nationality. He is particularly known for his plays Marat/Sade and The Investigation and his novel The Aesthetics of Resistance.

Peter Weiss earned his reputation in the post-war German literary world as the proponent of an avant-garde, meticulously descriptive writing, as an exponent of autobiographical prose, and also as a politically engaged dramatist. He gained international success with Marat/Sade, the American production of which was awarded a Tony Award and its subsequent film adaptation directed by Peter Brook. His "Auschwitz Oratorium," The Investigation, served to broaden the debates over the so-called "Aufarbeitung der Vergangenheit" (or formerly) "Vergangenheitsbewältigung" or "politics of history." Weiss's magnum opus was The Aesthetics of Resistance, called one of the "most important German-language work[s] of the 70s and 80s." His early, surrealist-inspired work as a painter and experimental filmmaker remains less well known.