The Space Kaiju are Kaiju who's origins come from outer space and are supposedly the oldest and strongest breed of Kaiju in existence.
It is unknown where each Space Kaiju occupies, but it is believed that they each were once under the control of different alien races during The Thousand Year War between the Xilians, Nebulans, Devonians, Kilaaks, Simians and Millennians that lasted thousands of years before being freed following the demise of their creators during the war.
It is believed that even one Space Kaiju is as strong (if not stronger) than Godzilla himself and is enough to wipe out an entire city. Many Space Kaiju have been shown to easily overpower the King of the Monsters in combat and lay waste to cities in relatively short time.
Known Space Kaiju include:
|King Ghidorah||An ancient space dragon that was responsible for the KT Extinction and the destruction of the rest of his race known as the King of Terror. During his battle with Godzilla in Antarctica in 2001, he disappeared after being struck by Dimension Tide and has not been heard from since.||Ghidorah||Unknown|
|DesGhidorah||An ancient space dragon and the younger brother of King Ghidorah known as the Demon of Mars. He was sealed away by Gigamoth during the events of the KT Extinction.||Ghidorah||Alive (Sealed)|
|Mecha-King Ghidorah||A member of the Ghidorah species that crash-landed on Terra thousands of years ago known as Guardian King Ghidorah before being turned into a cyborg by the Cryogs. After being heavily damaged following a battle with Godzilla and Anguirus, he disappeared after fleeing into space.||Cyborg King Ghidorah||Unknown|
|SpaceGodzilla||The extraterrestrial and genetically cloned brother of Godzilla. Following the invasion of the Cryogs and the Trilopods, he became the leader of the Earth Conquerors as a rival faction to the Earth Defenders.||Extraterrestrial Godzilla Clone||Alive|
|Monster X||A space monster once controlled by the Xillians before being freed following their destruction during the Thousand Year War. He was later killed by Godzilla during his invasion of Terra in 2008.||Xillian/Ghidorah Hybrid||Deceased|
|Gigan||A cybernetic dinosaur once controlled by the M-Space Hunter Nebula aliens before freed following their destruction during the Thousand Year War. He disappeared following his defeat during The Trilopod War.||Cybernetic Space Dinosaur||Unknown|
|Megalon||A cybernetic insect once controlled by the M-Space Hunter Nebula aliens. Sometime before the end of the war, Megalon was sent out on a mission and accidentally ended up on Terra, where he eventually fought King Caesar, causing the fall of the Ryukyu Kingdom and the fall of the second age of Guardian Kaiju.||Cybernetic Space Insect||Unknown|
|Hedorah||A Kaiju that was controlled by the Kilaaks during the Thousand Year War before being freed after their destruction during the war. He was supposedly killed following a battle against Godzilla and Super MechaGodzilla.||Smog Monster||Unknown|
|Orga||A Kaiju that was originally the Millennians who fought in the Thousand Year War before crash landing on Terra thousands of years ago and being taken to Area 51 before absorbing Godzilla's DNA and transforming in 2010. His pod was retrieved by the Cryogs before being launched off-planet following the Devonians betrayal.||Millennian/Godzillasaurus Hybrid||Unknown|
|MechaGodzilla||A mechanized Godzilla clone constructed by the Cryog Commander Rhizon during Godzilla's supposed death in 2010. A majority of them were destroyed by Godzilla and Anguirus, while another variant was constructed by the Simians.||Robot||Unknown|
|Magita||The Queen of the Trilopods that was let loose by Emperor of the Cryogs Karkaro during the Trilopod War. She was killed by Godzilla when he unlocked his Burning Mode.||Trilopod||Deceased|