Justiniana Prima is the name of a city built by Emperor Justinian I (527–565) to honour the place of his birth, whose momentous significance was decided when its Church was granted the rank of an independent archbishopric with its own province. Although a relatively large amount of written sources, confirming the existence of this city from 535 to the early 7th century, have survived, almost nothing is known about the city itself. This is equally true of the origins of Justiniana Prima, which are difficult to reconstruct, its functioning as a city, and its mysterious end. It is accepted in the literature on the subject that, when Byzantium lost its reign over a considerable part of the Balkans as a result of invasions and wars against the Avars and the Slavs during the rule of Heraclius (610–641), the city was probably abandoned and destroyed. Until the present day, it has been impossible to establish the undisputable location of the city, which is why everything that is known for certain comes from the written sources, the most significant of which are Emperor Justinian's Novels XI and CXXXI and Procopius of Caesarea's De aedificiis, in the part devoted to Emperor Justinian's native country.

The starting point for reconstructing the unknown aspects of Justinian's religious policy, which consisted in introducing changes in the ecclesiastical organisation by promoting cities where prefects resided, is an interpretation of Novel XI. The novel's very existence in the legal reality of the time clearly revealed the Emperor's goal of introducing changes in the ecclesiastical organisation on the highest level, concerning the jurisdiction of patriarchs; the establishment of the Archbishopric of Justiniana Prima is a trace of those changes. The uniqueness of Novel XI consists in:

The last issue is important but so far it has been completely overlooked. It is worth using the surviving summaries of Novel XI as a background in order to show how jurists at the time understood the essence of the change in the ecclesiastical organisation which this constitution introduced.