Gammera the Invincible

An atomic explosion awakens Gammera--a giant, fire-breathing turtle monster--from his millions of years of hibernation. Enraged at being roused from such a sound sleep, he takes it out on Tokyo.

Gammera the Invincible is a 1966 sci-fi family movie, starring Brian Donlevy, John Baragrey, Albert Dekker. It holds an IMDb rating of 5.0/10 from 1,484 votes and runs 1h 26m.