User blog comment:Radionatix/Is King Ghidorah Kaiju dragon or hydra??/@comment-3367060-20160101211918

He's... a Ghidorah. In his Showa version he's a space dragon, in his Heisei version he's a mutated trio of Dorats, and in GMK he's a premature Yamata no Orochi. So he has been a "dragon," but never been a Hydra. Saying Ghidorah is a Hydra is like saying Godzilla is a lizard.

Though, Ghidorah's name comes from the word 'Hydra' (Gidora -- Hidora).