The Joulion (ジュリオン, Jurion) is an enemy from the Metroid series.
Joulions have only appeared in Metroid: Other M. These floating creatures resemble water fleas, and were only found in the cold environments of the Cryosphere aboard the Bottle Ship. They attack Samus Aran with electricity, but will inflate and explode if she attacks them, which may result in a chain reaction of multiple Joulions exploding.
Joulions, along with Zeros and FG II-Graham units, appear as stage hazards on Pyrosphere. Joulions drop down towards the stage and then float in the air before automatically inflating and exploding after a short time. If attacked by a fighter, a Joulion is provoked into exploding prematurely; this can be used to deal damage to opponents or Ridley. The more damage a Joulion takes before exploding, the greater the strength of the explosion will be. Joulions do not appear when the stage is set to Ω form.