Justinian I (527–565) is one of the best-known rulers of Byzantium and without much doubt, one of the most outstanding Roman and Byzantine emperors ever. This is mainly due to his achievements. Military successes, the likes of which had not been seen for centuries, enabled the Empire to recapture its domains in Africa, Italy, and southern Spain. The number, size, and beauty of the buildings erected by Justinian filled his contemporaries with awe; many of them have survived to our times. The Emperor secured a permanent place in history for himself as a great legislator, even though religious matters were decisively closer to his heart. It should be emphasised that even if the laws he introduced were not always positively evaluated, the very fact that on his initiative the work on the Code was started contributed to the survival of numerous unique sources from the earlier period. On the other hand, the ruler's excessive and authoritarian involvement in ecclesiastical matters caused many serious internal problems, ranging from the revolt of the Samaritans, driven to the limit, to the desperate escape of pagan philosophers to Persia. Using state power to solve theological disputes which divided contemporary Christians also led to a ruthless persecution of opponents of the beliefs shared by the ruler and to bending the Church to his will.

We have to resign ourselves to the fact that it is very difficult to arrive at an unambiguous evaluation of the ruler's reign as a result of a great number of various events occurring during this period and Justinian's broad, multidimensional activity. An idealised image of a great emperor, conqueror and legislator, should not automatically be replaced with an image of a bloody persecutor of his religious opponents, who oppressed the majority of his subjects with high taxes. It is worth remembering that it was not insignificant (for the evaluation of both the entirety of Justinian's reign and of individual spheres of his activity) that he ruled for a very long time, and that a relatively large number of various sources from this period have survived.

Undoubtedly, the last few decades have seen a considerable progress in the studies on Justinian's times, which, however, cannot eclipse the need to further intensify such research.