Phase IV is an American science fiction film, made in 1974. It is the only feature-length film directed by the noted title designer Saul Bass. It starred Nigel Davenport, Michael Murphy, Lynne Frederick and Helen Horton (who would later provide the voice of "Mother" in Alien).

The film bears some similarity to the Poul Anderson's short science fiction novel Brain Wave and also to the earlier film, The Hellstrom Chronicle. Both feature extensive use of close-up photography of actual insects. Both imply that humanity, having failed, must give way to insects, who will now take over from them, in Hellstrom Chronicle insects generally, in Phase IV, ants specifically.

Due to some unknown cosmic event, listed in "phases", ants have undergone rapid evolution and developed a hive mind. A scientific team then begins investigating strange towers and geometrically perfect designs which the ants have started building in the desert. The ant colony and the scientific team, along with a rural family, make war with each other, with the ants making the more effective aggressors. The narrative uses the scientific team as the main protagonists, but also an ant "hero" going about his duties in the colony. The film concludes with the last of the cosmic "phases", Phase IV, which promises a new future for all life on Earth.

Despite the lurid tone of its poster art, Phase IV approaches its subject matter naturalistically, with relatively little melodrama. The film contains relatively little dialogue, mainly relaying the storyline visually.

Journalism student Simon Tate thinks it's strange when four students at the university suddenly die in "unrelated" accidents. When his friend, Dr. Benjamin Roanic, becomes the prime suspect and is suddenly murdered, Simon sets out to prove his innocence. He soon discovers the students were Roanic's test subjects in a secret drug test program, and had been cured of AIDS. He is forced to run for his life, when a pharmaceutical company tries to prevent him from revealing the truth behind "Phase IV". Written by Anonymous

Desert ants suddenly form a collective intelligence and begin to wage war on the desert inhabitants. It is up to two scientists and a stray girl they rescue from the ants to destroy them. But the ants have other ideas. Written by Nizam Ahmed