Ars Magica is a role-playing game set in 'Mythic Europe' – a historically grounded version of Europe and the Levant around AD 1200, with the added conceit that conceptions of the world prevalent in folklore and institutions of the High Middle Ages are factual reality. The players' involvement revolves around an organization of magi and their allies and foes both mundane and supernatural. The game was originally developed by Jonathan Tweet and Mark Rein-Hagen, with its first edition published in 1987.

Jonathan Tweet is an American game designer who has been involved in the development of the role-playing games Ars Magica, Everway, Over the Edge, Talislanta, the third edition of Dungeons & Dragons and 13th Age, and the collectible miniatures game Dreamblade. In 2015 Tweet released Grandmother Fish, a full-color, full-sized book about evolution aimed at preschoolers. In 2018 Tweet released Clades and Clades Prehistoric, two card games for children and adults which demonstrate the concept of a clade.