The Global Legend of Prester John delves into the enduring fascination with Prester John, an unreachable, collectively-imagined Christian priest-king who figured prominently in Europe's entrance into an interconnected global world. This Element draws on “The International Prester John Project,” an archive of Prester John narratives, from papal epistles to missionary diaries to Marvel comics, all of which respond to the Christian heterotopia promised in the twelfth-century Letter of Prester John. During the medieval and early modern periods, the desire to legitimize the letter's contents influenced military tactics and papal policy while serving as a cultural touchstone for medieval maps, travel narratives, and romance tales. By providing an overview of distinct narrative paths the legend took along with an analysis of the themes of malleability and elasticity within and across these paths, this Element addresses how belief in Prester John persisted for six centuries despite a lack of evidence.