The name Dark is used to refer to several different concepts in the Kingdom Hearts series:
- The primal force, associated with the heart
- The realm composed of that force
- The Keyblade of that realm
- The door between that realm and the Realm of Light
- The Dark Meridian between that realm and the Realm of Nothingness
- The corridors used to move between those realms
- The Portal of Darkness areas within the World of Chaos
- The Dark Depths area in Radiant Garden
- The Darkside Heartless from Kingdom Hearts
- The Dark Thorn Heartless from Kingdom Hearts II
- The Dark Follower Heartless from Kingdom Hearts 358/2 Days
- The black material type from Kingdom Hearts II
- The Dark Matter synthesis material from Kingdom Hearts Final Mix
- The Dark Ring accessory from Kingdom Hearts
- The Dark Anklet accessory from Kingdom Hearts II
- The form Roxas's Keyblade takes when equipped with the Hazard Gear
- The form Riku takes when channeling the power of darkness
- The ability granted by the Two Become One Keyblade