House III: The Horror Show (also known simply as House III or The Horror Show) is a 1989 American slasher film directed by James Isaac, from a script co-written by Allyn Warner and Leslie Bohem. Produced by Sean S. Cunningham, it serves as the third installment in the House film series. Presented as a standalone installment in the series, it stars Lance Henriksen and Brion James in the lead roles. Centering around Detective Lucas McCarthy, who arrests a serial killer known as Max "The Cleaver" Jenke; the plot revolves around the latter's return from the dead as a malicious spirit to terrorize the detective and his family in their house.

Detective Lucas McCarthy finally catches serial killer "Meat Cleaver Max" Jenke and watches his execution. McCarthy is shocked to see the electric chair physically burn Max before he finally dies promising revenge. Max has made a deal with the devil to frame Lucas for his murders from beyond the grave. Max scares the McCarthy family (who have moved into a new house) and the parapsychologist Peter Campbell they hired. Campbell tells Lucas that the only hope of stopping Max for good is to destroy his spirit.

As the family move in, Donna searches the basement to find their missing cat Gazmo. The furnace turns on and the door flings open; apparently Max's spirit is inside the house and focused on the basement. Lucas starts having hallucinations that lead him to behave erratically. Bonnie goes to the cellar to secretly meet her boyfriend Vinnie, who is later killed by a physical manifestation of Max with a cleaver. The next night, Bonnie tells Scott to come with her to look for Vinnie, while Lucas goes to the basement and angrily calls for Max to stay away from his family. Bonnie returns to the basement and finds Vinnie's body for which Lucas is suspected of the murder.

Max kills Scott with the meat cleaver, transforms into Bonnie and decapitates Campbell before holding Donna hostage. Lucas escapes from questioning and goes into the cellar to fight Max. Lucas sends Max to the electric machine where his arm gets stuck, Lucas and Donna use the chair to shock Max causing him to appear back in physical form in the house where Lucas shoots him dead.

The next day the McCarthys are moving out with Scott still alive. Bonnie goes into the basement and runs outside to find Gazmo in a box. The family takes a photo as the screen freezes and fades to black.

Fred Walton was initially slated to direct the film, but disagreements between him and producer Sean S. Cunningham led to Walton departing the project.

Director David Blyth was replaced by James Isaac a week into shooting as Cunningham was dissatisfied with the dailies. Allyn Warner is credited as writer for the film as Alan Smithee.

The Horror Show was originally developed as an entry into the House film series, but was marketed within the U.S. as unrelated, as the producers felt that it differed greatly and was a traditional horror movie compared to the comedic earlier installments. Despite this, the film kept its original title and was released as House III: The Horror Show outside of the U.S. market. Cunningham was further motivated to distance the film from the House name as House II: The Second Story failed to match the success of its predecessor. Matters were further complicated by the fact the original screenplay was written to be more in tone with the prior House films and included the signature surreal humour, and as part of distancing the film from the House name the script was being reworked during production which was attributed to the accelerated schedule distributor MGM/UA placed the film on.