Inseminoid (titled Horror Planet in the United States) is a 1981 British science fiction horror film directed by Norman J. Warren and starring Judy Geeson, Robin Clarke and Stephanie Beacham, along with Victoria Tennant in one of her early film roles. The plot concerns a team of archaeologists and scientists who are excavating the ruins of an ancient civilisation on a distant planet. One of the women in the team (Geeson) is impregnated by an alien creature and taken over by a mysterious intelligence, driving her to murder her colleagues one by one and feed on them.

Inseminoid was written by Nick and Gloria Maley, a married couple who had been part of the special effects team on Warren's earlier film Satan's Slave. It was filmed between May and June 1980 on a budget of £1 million (£5 million in 2023), half of which was supplied by the Shaw Brothers. The film was shot mostly on location at Chislehurst Caves in Kent as well as on the island of Gozo in Malta, combined with a week's filming at Lee International Studios in London. Composer John Scott completed the film's electronic musical score over recording sessions that lasted many hours.

Despite a good box office response in the UK and abroad, Inseminoid failed to impress most commentators, who criticised the effects and production design. The overall quality of the acting was also poorly received, although Geeson's performance was praised. Criticism was also directed at the premise involving an alien insemination, which some commentators saw as a weak imitation of Alien (1979). Both Warren and 20th Century Fox, distributor of Alien, rejected claims that Inseminoid was influenced by that film.