- Classification: Alien
- Homeland: Planet Sokonashi
- Choujin Kyoudo: 200,000 Power(?)
- First Appearance: Manga Chapter 20
Sokonashi-seijin (底無し星人, Bottomless Alien) is an alien who devours everything in his path, including Kinnikuman and Natsuko. Kinnikuman eventually escapes after cutting Sokonashi-seijin's stomach open with his Kinniku Cutter. He later reappears as one of Kinkotsuman's minions.