"Those without hearts." -Leon describing The Heartless
Heartless are living creatures manifested from the darkness in people's hearts. They go around collecting hearts coming in many forms and types of Heartless. Their weakness is the Keyblade, which Sora, Riku, Kairi, Jeffrey, Nathan, Mitsuki, Xion, Aqua, and King Mickey Mouse wield. Maleficent and other villains used the Heartless for their own evil ends.
- Jaden will first fight the Heartless in The Jaden Sora Power Hour.
- The Heartless will appear in Jeffrey, Jaden & Friends' Storm Adventures of Scooby Doo 2: Monsters Unleashed.
- The Heartless will appear again in Jeffrey, Jaden & Friends play Jumanji.
- Several Heartless guest star in Jeffrey, Jaden & Friends' Storm Adventures of Goosebumps.
- The Heartless will become Aaron's enemies throughout Aaron's Adventures Series.
- Dogbert and Rat have a secluded lab onboard the Liver of Iron where the experiment on Heartless.
- The Heartless will appear as recurring enemies in Twilight's Adventures Series.