This book explores one of the most significant medieval saints' cults, that of St. Maurus, the first known disciple of Saint Benedict. Despite the centrality of this story to the myth of medieval Benedictine culture, no major scholarly work has been devoted to Maurus since the late nineteenth century. Drawing on memory studies, this book investigates the origins and history of the cult, from the ninth-century Life of St. Maurus by Odo, abbot of Glanfueil, to its appropriation and re-shaping by three powerful abbeys through to the thirteenth century-Fosses, Cluny, and Montecassino. It traces how these institutions deployed caches of mostly forged documents (many translated here for the first time) to adapt the cult to their aspirations and, moreover, considers how the cult adapted itself further, to face the challenges of the modern world.