Justinian
Justinian I (ca. 482-565) was the greatest empire of the Eastern Roman (or Byzantine) Empire. He ruled from 527 until his death. Justinian was preceded by Justin I and succeeded by Justin II. He was the husband of the famous Empress Theodora.
He is best known for his military succeses, as he regained most of the territory of the old Roman Empire in Africa and Italy. He also is famous for the writing of Justinian's Code, the law code that is the basis of modern law.
Justinian is a saint of the Eastern Orthodox Church. He was a Christian emperor, yet he encouraged the persecution of Jews, even creating a ghetto in Constantinople. He also backed the orthodox clergy in denouncing other Christians as heretics. He constructed the Hagia Sophia, which was one of the most magnificent and beautiful buildings ever, until the muslims turned it into a mosque.
A much different view of Justinian and wife is given in Procopius' A Secret History, which portrays him in a very negative light.
References
Holmes, George. The Oxford Hisory of Medieval Europe. Oxford: University Press, 1988.