Mark Rein-Hagen, stylized as Mark Rein•Hagen, is an American role-playing, card, video and board game designer best known as the creator of Vampire: The Masquerade and its associated World of Darkness games. Along with Jonathan Tweet, he is also one of the original two designers of Ars Magica.

Vampire: The Masquerade is a tabletop role-playing game created by Mark Rein-Hagen and released in 1991 by White Wolf Publishing as the first of several Storyteller System games for its World of Darkness setting line. It is set in a fictionalized "gothic-punk" version of the modern world where players assume the role of vampires, who are referred to as "Kindred." and deal with their night-to-night struggles against their own bestial natures, vampire hunters, and each other.