An expedition in the South Pacific lands on a tropical island where the natives worship the mysterious deity Gappa. An earthquake opens up an underground cavern and a baby reptile is discovered inside. The natives warn the foreigners to leave the hatching alone, but they don't listen and take it back to a zoo in Japan. Soon after, moma and papa Gappa start smashing Tokyo looking for their kidnapped child.
- Original title: 大巨獣ガッパ
- Release date: April 22, 1967
- Status: Released
- Genres: Horror, Science Fiction
- Runtime: 1h 24min
- Producers: Nikkatsu Corporation