The social importance of saints’ relics during the European Middle Ages is well documented, yet relics have rarely been treated as mobile objects beyond discussions of their transportation from one permanent location to another (a “translation”). This dissertation examines the practice of taking relics on out-and-back journeys to explore the consequences of temporarily removing these objects from the churches in which they were housed and displayed, focusing on northern France and the Low Countries during the high Middle Ages. Medieval relics were considered direct conduits to the supernatural power of the saints, and an itinerant relic projected religious, economic, and political authority onto the areas it traveled through. However, travel also brought a relic into contact with unfamiliar audiences. Using evidence from customaries, hagiography, charters, and images, I demonstrate that while moving relics transformed them into versatile tools of power, it also exposed them to criticism, antagonism, and danger from both lay and ecclesiastical groups. The first chapter argues that relics traveled frequently and regularly by tracking the appearance of instructions for temporary relic movement across eleventh-century customaries, mainly from the monastery of Cluny. The next three chapters examine hagiographical texts to reveal the complexity of the interactions between those performing relic journeys and three groups that they might encounter en route: other ecclesiastics, lay property owners, and the laity at large. The second chapter shows that while bringing their relics together could serve as a demonstration of goodwill between multiple monasteries, moving one relic into the physical presence of another might also provoke intense conflict. The third chapter examines the roles mobile relics could play in monastic property disputes, ranging from intimidation of lay opponents to more subtle assertions of authority over a landscape. The fourth chapter demonstrates that although medieval lay devotion to relics is often taken for granted, a mobile relic might also incite dissent or rejection from local laypeople. Finally, the fifth chapter explores visual and textual imaginings of relic journeys and their significance, especially the use of the Ark of the Covenant as a motif to valorize the experience of transporting relics.