Godzilla is a gargantuan-sized monster which inhabits the oceans of planet Earth, originating from off the coast of Japan. However, the name has been borne by more than one individual creature over the course of history.
The name "Godzilla" was originally used by the natives of Odo Island (whose folklore contains stories about such creatures) to identify a 50-meters-tall prehistoric reptile which emerged from the sea after being disturbed by nuclear bomb tests in 1954, and which fed on radiation and demonstrated the ability to discharge a powerful atomic breath from his mouth. This original monster was ultimately killed by the Oxygen Destroyer, invented by Dr. Daisuke Serizawa. Following this incident, there have been numerous other individuals, which have varied in size, abilities, origin, disposition and intellectual capacity. Some have been quite friendly and heroic, while others remain wild and brutally destructive, laying waste to entire cities during rampages.
Notably, the more heroic incarnations of Godzilla have often found themselves involved with defending the Earth against numerous extraterrestrial threats, including but not limited to: King Ghidorah, Gigan, Hedorah, the Kilaakians, the Energy Beast, among others. Additionally, Godzilla's appearance has been used as a template by the Black Hole Planet 3 Aliens to create Mechagodzilla, and parts of his DNA which have accidentally found their way to space (via either Biollante or Mothra) ended up spawning the aberration known as SpaceGodzilla.