Gaira (ガイラ), also just called the Green Gargantua, is a giant green humanoid monster that appeared in the 1966 Toho film War of the Gargantuas.
Gaira looks like a giant green human with a noticeable underbite and what appears to be seaweed growing all over his body. Gaira is 25 meters tall and weighs 10,000 tons.
Gaira is a spawn of Frankenstein's Monster that resulted from some of Frankenstein's cells being deposited underwater and regenerating back into a full body. Unlike his gentler brother Sanda, Gaira was subjected to a harsh underwater environment filled with hostile sea creatures and grew up to be cruel and hateful.