Jack is a given name, but also a name used by one of the members of the Royal Flush Gang.
- Jack, member of the first, Cadmus-originated Royal Flush Gang.
- Jack, a man recruited by Ace.
- Jack, member of the Walker Family.
- Jack, victim of the Sewer King.
- Jack, officer in "A Touch of Curaré"
- Jack Napier, an alias used by the Joker before his disfiguration.
- Jack Ryder, the Creeper
- Jack Turley, boxing coach.
- Jolly Jack Candy Factory
Other people named Jack':