From a western Mediterranean point of view, the reign of Justinian may seem a brief parenthesis in the history of Europe, a failed attempt to resurrect an empire already dead. Justinian’s reconquest of Italy was brought to nothing by the Lombard invasion of 568, and North Africa fell to Muslim armies within a century. From a Roman ecclesiastical perspective the balance sheet is even more negative. The sad story of the Three Chapters Controversy and the souring of relations between Constantinople and Rome contributed greatly to Justinian’s reputation for divisive autocracy in ecclesiastical affairs. This chapter does not seek either to defend the western attitude toward Justinian’s religious politics or to clear his name. Instead it explores the “parting of the ways” between West and East signaled by these differing ecclesiastical perspectives. In Justinian’s day there was still no consensus about the emperor’s place in Christian society, and the question of the relations between church authority and political power played a major role in the parting of East and West, especially in the West, where imperial power was weak. The eclipse of imperial authority in the West during the fifth century created new conditions for its churches and demanded new definitions of their relation to the emperor. Even in times of tension, Rome and Constantinople desired the unity of church and empire and the defense of Christianity, but the assumptions underlying these diverged significantly. The reunion of the western provinces with Constantinople during Justinian’s reign highlighted and even reinforced these differences. Seeing the Age of Justinian as a major phase in this process of separation gives new insights on the Roman church and the complex history of its relations with Constantinople.