The Green Slime (Japanese: ガンマー第3号 宇宙大作戦, Hepburn: Ganmā Daisan Gō: Uchū Daisakusen, lit. 'Gamma 3: The Great Space War') is a 1968 tokusatsu science fiction film directed by Kinji Fukasaku and produced by Walter Manley and Ivan Reiner. It was written by William Finger, Tom Rowe and Charles Sinclair from a story by Reiner. The film was shot in Japan with a Japanese director and film crew, but with the non-Japanese starring cast of Robert Horton, Richard Jaeckel and Luciana Paluzzi.

After destroying a huge asteroid that was on a rapid collision course with Earth, a group of astronauts discover they have accidentally returned to their space station with an alien slime creature that feeds on radiation and can reproduce rapidly from its own blood.