Home world: Earth (Nebula M78 Universe)
First appearance: Return of Ultraman episode 11 "Poison Gas Monster Appears" (1971)
Latest appearance: None
Height: 47 m
Weight: 24,000 t
Category: Kaiju
Affiliation: None
Roar(s): TBA

Mognezun (モグネズン Mogunezun) was a kaiju that appeared in the TV series, Return of Ultraman, episode 11.

Subtitle: Poison Gas Monster (毒ガス怪獣 Dokugasu Kaijū)


  • Height: 47 m
  • Weight: 24,000 t
  • Tail length: 60 m 
  • Origin: Underground Nishinosawa 


Return of Ultraman

Mognezun was a monster who had been feeding on the Yellow Gas (a real life world war II weapon) dumped by Japan's Army, giving the monster his poisonous gas powers. Mognezun used his gas to attack trespassers who neared his territory, often disappearing before MAT could react or arrive. However MAT watched a film that was at the scene and showed that a entire film crew dying at the hands of the gas.

After taking out one of MAT's members, the rest of MAT tried to take care of the situation. At first they seemed to get the advantage by placing a giant muzzle over Mognezun’s dangerous mouth, but Mognezun eventually pried it off and sprayed his gas at Goh. Luckily Ultraman Jack appeared and the two fought. While Ultraman tried to fight the monster, Mognezun used his poisonous spikes to paralyze Jack and started poisoning Jack with his gas. MAT quickly returned with a new weapon, a gas machine that exhaled a white gassy substance that made Mognezun's poison flammable. Jack proceeded with firing the Specium Ray and igniting the gas. With Mognezun's gas effect nullified, Ultraman Jack was able to regain control of the fight and ultimately struck Mognezun in the head with his Meteor Kick, causing Mognezun to keel over and die.


  • Suit actor: Toya Takanobu
  • Mognezun's roar is a slowed down Kiyla roar.
  • Although not physically seen, Mognezun is one of the monsters that makes up Beryudora's body in Mega Monster Battle: Ultra Galaxy Legend The Movie.
  • Mognezun shares the same subtitle as Kemular.
  • Mogunezun was meant by screeenwriter Tetsuo Kinjo to be a commentary on Japanese usage of chemical weapons in the Second World War, which is most evident in the monster's consumption of mustard gas.

Powers and Weapons

  • Poison Gas: Mognezun can expel a yellow poisonous gas from his mouth. It is powerful enough to kill humans in seconds. Use on ultras can cause disorientation.
  • Spikes: Mognezun's back is covered in spikes, touching them can temporarily shock/repel opponents.
  • Burrowing: Mognezun can burrow at moderate speeds.



Return of Ultraman Kaiju & Seijin
Takkong | Zazahn | Arstron | Sadola | Detton | Kingsaurus III | Gudon | Twin Tail | Gorbagos | Ghostron | Dangar | Stegon | Mognezun | Shugaron | Seamons | Seagorath | Eledortus | Terochilus | Bemstar | Sartan | Magnedon | Beacon | Gokinezula | Zanika | Vacuumon | Kupukupu | Kingstron | Zagorath | Nokogilin | Gronken | Varricane | Yadokarin | Oxter | Plooma | Alien Zelan | King Maimai | Alien Mates | Muruchi | Leogon | Pris-Ma | Draculas | Re-Seagorath | Re-Bemstar | Black King | Alien Nackle | Alien Varduck | Alien Black | Snowgon | Alien Baltan. Jr | Builgamo | Alien Stora | Paragon | Alien Grotes | Kodaigon | Granadas | Alien Centaurus | Robonez | Alien Cygnus-61 | Alien Messie | Alien Zoole | Red Killer | Femigon | Yametaranese | Sasahiller | Alien Ateria | Alien Mysteler | King Bockle | Alien Bat | Zetton II