A type of space Kaiju that is tremendously heavy for its size, that spends most of its time asleep.

Skydon falls from space becoming meteorite-like and lands on the reclaimed land in Tokyo’s Harumi district where it creates a deep crater. It emerges from the crater and causes the ground to shake violently as the SSSP arrives to investigate. Realizing Skydon primarily stays asleep and won't attack unless provoked, SSSP tries to carry Skydon back into space using “Operation Wire Lock”. However, Skydon is too heavy and before it can be even lifted off the ground one of the Jet VTOLs breaks. Ultraman appears and tries to attack it, but Skydon doesn’t even stir as all of Ultraman’s attacks are useless against its immense weight and incredibly dense armored shell.

The SSSP tries several other ideas but they all end in failure. Their final plan, “Operation Monster Balloonization” sees the team fill Skydon with helium. Skydon miraculously floats skywards but is targeted by Air Defense Force jets on a training exercise and begins to fall back to Earth. Ultraman attacks it with an Aerial Body Strike which causes Skydon to explode.