Psycho – The granddady of real-life horror monsters would have to be Ed Gein, the small town serial killer who partly inspired novelist Robert Bloch to write the novel that eventually became Alfred Hitchcock’s Psycho.

The Texas Chainsaw Massacre – Gein was also a big point of inspiration for the Psycho of the 70s.

Deranged – Ed Gein once again inspired this 1970s horror film, leading one to wonder if anyone in his family ever tried to sue for royalties.

The Girl Next Door – Unlike Psycho or TCM, The Girl Next Door hews to a real-life case relatively closely, that of the murder of Sylvia Likens.

The Strangers – Most home invasion thrillers probably draw from real life at some point, this one in particular was inspired by probably the most famous home-invader of them all: Charles Manson.

Eaten Alive – Tobe Hooper’s follow-up to The Texas Chainsaw Massacre was based on another real-life Texas killer: Joe Ball, aka The Alligator Man.

Wolf Creek – As frightening as it is, Wolf Creek is indeed based on real crimes committed by Ivan Milat and Bradley John Murdoch.

B.T.K. – Arguably the scariest serial killer of recent vintage is the BTK (short for Bind, Torture, Kill) Killer Dennis Rader, the inspiration for the horror biopic B.T.K.

Curse of the Zodiac – More respectable films have been inspired by the serial killer known as Zodiac, but this is the grimy horror movie answer to the Fincher movie.

Gacy – Crimes don’t get much more tailor-made for horror movies than those committed by notorious killer clown John Wayne Gacy.

Henry: Portrait of a Serial Killer – The crimes and delusional fantasies of Henry Lee Lucas were the primary source of inspiration for this lastingly infamous horror movie.

The Black Dahlia – Much of Brian De Palma’s 2005 film is devoted to a fictional detective plot, but the case at the center of it all – the still-unsolved murder of Elizabeth Short – is all too real.

The Dentist – Allegedly based on a real dentist-turned-serial-killer (or is that vice versa?), this is a movie to avoid if you’re already afraid of the dentist.

Borderland – Real-life cult leader Adolfo de Jesús Constanzo and the human sacrifices performed by his cult were the inspiration for this 2007 movie.