The Monster Graveyard (怪獣墓場 Kaiju Hakaba) is a location in the Ultra Series. It is the burial grounds of all the fallen monsters and aliens whom had been killed by the Ultra Warriors over the centuries or Space Monster Bemular who live here.
Not many details have been mentioned, but what is known that the Monster Graveyard is a distortion of spacetime that is located somewhere in the universe. The Monster Graveyard acts as an afterlife for the monsters, aliens, and sentient beings (both good and bad) whom have been defeated by the Ultra Warriors or other monsters throughout the centuries. When any opponent is destroyed, their soul is lifted and sent to the Graveyard, where their bodies would be reconstructed. The creature, however, is forced to reside in the Graveyard for the rest of eternity, unless it is revived by an outside source. It has also been shown that native monsters at rest desire to stay in this place, such as when Seabozu was taken out but immediately wanted to go back. It can be shown that the Monster Graveyard acts as a Heaven to monsters. It was also stated that the graveyard was the only place where a monster can find true peace.
- In the original Ultraman series, The Monster Graveyard is first seen by SSSP where they discover Seabozu headed for Earth, along with several deceased monsters.
- In The☆Ultraman, the Babaloneon Empire stated that all the monsters under their control were revived from the Monster Graveyard.
- In the Ultraman 80 series, the kaiju, Myu, was taken from his home in the Monster Graveyard to Earth.
- In the Ultraman Mebius series, GUYS travels to the Monster Graveyard after receiving a distress signal coming from it. There they find a pair of Lesser Bogars that somehow wandered in.
- In the film Mega Monster Battle: Ultra Galaxy Legends The Movie, the climax takes place in the Monster Graveyard involving Ultraman Belial and his 100 Monster Army versus the remaining Ultra Brothers and the ZAP SPACY.
- In the film Ultraman Saga, Alien Bat stated that he took the souls of Gubila, Gomess, and Arstron as his first test subjects from the Monster Graveyard.
- The events of Ultra Zero Fight A New Power take place in the Monster Graveyard.
- Grave Gate: The Gate into the Monster Graveyard. Said to be 600,000 years old, it is recognized by its design of 3 gigantic rings looped around one another in a trefoil knot.
- Ultra Zone: This space distortion acts as a temporary gateway to the Monster Graveyard. It occurs randomly and can only be accessed through the distortion portal. Beings like Lesser Bogar are able to create portals to travel to and from the Ultra Zone. This is the method used by the SSSP, UGM, and GUYS when they traveled to the Monster Graveyard.
- Floating Continent: The Floating Continent is the massive area within the Graveyard in which the souls of the monsters and aliens whom had died (either in battle or by other means) reside in peace. It was also the destination in which the Ultra Brothers fought the revived Dark Four Heavenly Kings, as well as where the climax of the Ultra Galaxy movie took place.
- Valley of Flames: The Valley of Flames is a river of magma that resides within the Floating Continent. Deep beneath the magma is a tubular pathway of fire that encompasses a narrow pathway that leads to the weapon, the Giga Battle Nizer, which was sealed away by Ultraman King and guarded by an EX Zetton.
While the Monster Graveyard is primarily host to the spirits of fallen monsters and aliens, a set of monsters are also known to live there without being dead.