Mark of the Devil (German: Hexen bis aufs Blut gequält, lit. Witches Tortured Till They Bleed) is a 1970 West German historical horror film directed by Michael Armstrong, and starring Olivera Vučo, Udo Kier, Reggie Nalder, Herbert Fux, and Herbert Lom. Its plot follows a witch hunter in 17th-century Austria who begins to question his pursuits after witnessing a rogue witch hunter dubiously accuse the townspeople of a small village, and employ increasingly sadistic methods of torture against them.

It is most remembered for US marketing slogans devised by Hallmark Releasing Corp. that included "Positively the most horrifying film ever made" and "Rated V for Violence", while sick bags were given free to the audience upon admission.

While not prosecuted for obscenity, the film was seized and confiscated in the UK under Section 3 of the Obscene Publications Act 1959 during the video nasty panic.