Cat in the Brain (Italian: Un gatto nel cervello (I volti del terrore)) (lit. A cat in the brain), also known as Nightmare Concert, is a 1990 Italian horror film written and directed by Lucio Fulci. Fulci stars as a fictionalized version of himself, a tortured horror filmmaker who is driven by the violent visions that he experiences both behind the camera and off the set. Feeling like he's losing his grip on reality and disturbed by murderous fantasies, Fulci consults a psychotherapist, who is secretly a serial killer and using hypnosis, exploiting the director's vulnerabilities to his own murderous ends.

A Cat in the Brain has been called the horror film equivalent of Federico Fellini's 8½, using cynical, Grand Guignol humour. Juxtaposing gory horror clips from several of his own past horror films which he had worked on, Fulci shot a wrap-around segment featuring his own plot and used Vincenzo Tomassi's film editing to create the storyline – a personal insight into the effects of horror filmmaking on the psyche.