This was one of director Ishirō Honda's last monster movies, and the first such movie made after the death of special-effects director Eiji Tsuburaya. Teisho Arikawa did the special effects for this film. While some fans deride the film as a last gasp of the kaiju eiga genre, others appreciate the fact that the monsters have been scaled down (only being 20 to 30 meters tall), making their interactions with human characters more compelling.
A space probe, dubbed "Helios 7", is sent to study Jupiter. En Route to the planet, the probe is invaded by Yog, an extraterrestrial being of pure energy. The probe lands in the South Pacific, where the disembodied alien leaves the device and invades the body of a Gezora, a giant cuttlefish, which proceeds to wreak havoc. When a photographer named Kudo and a small entourage landed on Selga Island, they are likewise menaced by Gezora. Gezora can generate extremely cold temperatures with its body, either naturally or due to Yog. When it is discovered that Gezora is vulnerable to fire, Kudo and his allies use a leftover Japanese World War II munitions cabin discovered on the island to set the monster aflame. Severely burned, the creature retreats to the water.
However, Yog continues its attack by similarly invading and controlling the bodies of two other rare giant creatures, a gigantic crab called Ganimes and a gigantic predatory water turtle called Kamoebas. The two monsters are coaxed into battling each other through the use of bats' natural sonar, which Yog has an aversion to. The two monsters stumble into an erupting volcano and meet their end, destroying Yog in the process.
- Toho Co. Ltd.: Japanese (84 min.; original version)
- Toho International: English (84 min.; International dub; released to DVD in America by Media Blasters)
- American International Pictures: English (84 min.; Titra dub; released in American theaters and VHS; titled Yog—Monster from Space.)
- Production Designer - Takeo Kita
- Assistant Director - Seiji Tani
- Chief Assistant Special Effects Director - Teruyoshi Nakano
- Special Effects Cinematographer - Yoichi Manoda
- Optical Effects - Yoshiyuki Tokumasa
- Special Effects Set Director - Yasuyuki Inoue
Actor's name on the left, characters played on the right.
- Akira Kubo - Taro Kudo, Journalist
- Atsuko Takahashi - Ayako Hoshino
- Yukiko Kobayashi - Saki, Daughter of Island Selgio
- Kenji Sahara - Makoto Obata
- Yoshio Tsuchiya - Dr. Kyouichi Miya, Biologist
- Tetsu Nakamura - Onbo, Elder of Island Selgio
- Yuu Fujiki - Mayor of publicity department of company 『Asia development』
- Yoshitake Saitou - Riko, Youth of Island Selgio
- Yuuko Sugihara - Stewardess
- Sachio Sakai - Chief editor of Weekly magazine 『Topics』
- Tyoutaro Tougin - Yokoyama, Investigation engineer
- Wataru Oomae - Sakura, Investigation engineer
- Ichiro Murakoshi - Voice of Alien
- Haruo Nakajima - Gezora and Ganimes
- Haruyoshi Nakamura - Kamoebas
- Akira Ifukube experimented with synthesizers for the first time here.
- This is the only time Haruo Nakajima portrays two kaiju in one film.
- On the poster, Gezora is seen fighting Kamoebas, although the two beasts never come in contact.
- The three monsters appeared in episode 57 of Keroro Gunso, though their origins are different.
- Space Amoeba was the last non-Godzilla movie to be directed by Ishiro Honda.
- Space Amoeba is widely considered to be the last kaiju eiga filmed in the classic style.