Killer Nun (Italian: Suor Omicidi, lit. Sister Murders) is a 1979 Italian nunsploitation horror film directed and co-written by Giulio Berruti, co-written by Alberto Tarallo, and starring Anita Ekberg, Joe Dallesandro, Lou Castel, and Alida Valli. Its plot follows a nun who, after recovering from brain surgery, grows increasingly paranoid that her health is again declining; she begins indulging in opioids from the hospital in which she works, and spirals into addiction and madness with violent consequences. The film is loosely based on the true story of Cécile Bombeek, a middle-aged nun who committed a series of murders in a geriatric hospital in Wetteren, Belgium in 1977.

The film was originally banned in Britain as a "video nasty" and released with cuts in 1993, but was finally released uncut on DVD in the UK during 2006, after changes in British censorship policy.