Peter Ulrich Weiss (8 November 1916 – 10 May 1982) was a German and Swedish writer, painter, graphic artist, and experimental filmmaker.

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, the latter of which has been called one of the "most important German-language work[s] of the 70s and 80s."