Mark Rein·Hagen (often written Rein-Hagen) is a role-playing, card, video and board game designer. Mark Rein·Hagen is best known as the creator of Vampire: The Masquerade and its associated World of Darkness games.
Rein·Hagen is also one of the original two designers of Ars Magica along with Jonathan Tweet. His work on World of Darkness has influenced the movie-series Underworld, True Blood, and otherkin sub-cultures such as Real Life Vampires and Real Life Werewolves.