Caltiki – The Immortal Monster (Italian: Caltiki, il mostro immortale) is a 1959 black-and-white science fiction-horror film with similarities to The Blob that was released in the previous year. The film's storyline concerns a team of archaeologists investigating Mayan ruins, who come across a creature that is a shapeless, amorphous blob. They manage to defeat it using fire, while keeping a sample of the creature. Meanwhile, a comet, which previously passed near the Earth around the time of the collapse of the Mayan civilization, is due to return, raising the possibility of a connection between the creature and the comet.

After the success of their film Hercules (1958), Galatea Film began production on films in other genres that they hoped would entice the international market, which led to Riccardo Freda being hired to direct Caltiki – The Immortal Monster. Freda left the project during filming, later explaining that he wanted to give his friend Mario Bava, who had been hired as the film's cinematographer and special effects artist, a chance to direct and earn more on the project. In interviews given long after the release of the film, both Freda and Bava gave conflicting opinions on who should be considered the real director of Caltiki. Various historians and ministerial papers suggest that Bava did create a large amount of footage of the film involving death scenes, the monster, matching shots and special effects scenes.

The film was released in Italy on 8 August 1959, where it grossed less than Bava's and Freda's previous genre collaboration I Vampiri.