Hermann Nitsch (born 29 August 1938) is an Austrian artist who works in experimental and multimedia modes.

Born in Vienna, Nitsch received training in painting during the time he studied at the Wiener Graphische Lehr-und Versuchanstalt. He is called an "actionist" or a performance artist. He is associated with the Vienna Actionists, and like them conceived his art outside traditional categories of genre. Nitsch's abstract splatter paintings, like his performance pieces, established a theme of controlled violence, using bright reds, maroons, and pale greys that communicate organic mutilation. In the 1950s, Nitsch conceived of the Orgien Mysterien Theater (which roughly translates as "Theatre of Orgies and Mysteries"), staging nearly 100 performances between 1962 and 1998.

Nitsch's work, which can be considered both ritualistic and existential, first drew attention in the early 1960s when he exhibited a skinned and mutilated lamb. The lamb was crucified against a white fabric-covered wall, with the entrails removed and displayed below a white table, splashed with blood and hot water. This was accompanied by Nitsch's "Geräuschmusik". Nitsch's subsequent work has incorporated many similar elements, often combining slaughtered animals, red fruits, music, dancing, and active participants. Nitsch juxtaposed slaughtered animal intestines with quasi-religious icons such as staged crucifixions, satirizing and questioning the moral ethics of atavistic religion and sacrifice. Currently his work is often discussed in the context of our cultures fixation with violence seen on the news, movie screens, and in popular video games. Correlations have also been drawn to many instances of the intersection of violence and culture. These performance works, which have become known as "actions" have become more and more elaborate over the years. This highly elaborate work is exemplified by the 6-Day Play, which Nitsch considered to be his pinnacle piece.

In 1998, Nitsch staged his 100th performance (named the 6-Day Play after its length) which took place at his castle in Austria, Schloss Prinzendorf. In 2004, he held an abbreviated (2-day) version of the work.

By 1995 Nitsch had been so sufficiently embraced by the establishment, that the Vienna State Opera invited him to direct and design the sets and costumes for Jules Massenet's opera Hérodiade.

Nitsch continues to publish articles and release CDs.