The early Christian cults of saints and relics as well as the act and process of pilgrimage were central themes in the religious practice of the Middle Ages. The veneration of saints and relics, the belief in miracles, and the act of pilgrimage were aspects of Christianity rapidly adopted by the converted population of the North Atlantic. This thesis focuses on St Magnus, Earl of Orkney († c. 1116), the cult and pilgrimage process which emerged about a century after the conversion of the Northern Isles. The physical monuments and primary sources, are seen as defining the cult, the pilgrimage process, as well as outlining a trace of the route. St Magnus cult and pilgrimage are also discussed within a comparative context; of the Norse cultural sphere, and of the medieval Universal Church.