List of Byzantine Emperors

The list of Byzantine emperors excludes numerous co-emperors (symbasileis) who never attained sole or senior status as rulers, and various usurpers or rebels who claimed the imperial title.

The first Emperor of the Byzantine Empire was Constantine the Great, the first Christian Roman Emperor, who founded Constantinople, and who was regarded by the later Byzantine Emperors as the model ruler. His predecessor Diocletian is sometimes considered the first "Byzantine" Emperor in a political sense, as he replaced the republican trappings of the Principate with the absolutist Dominate, a more typically oriental and Hellenistic form of autocratic monarchy that would characterize the Empire.

It was under Constantine, however, that the major characteristics of the Byzantine state emerged: a Roman polity centered at Constantinople and culturally dominated by the Greek East, with Christianity as the state religion.

All Byzantine Emperors regarded themselves as "Roman Emperors," the term "Byzantine" being coined by Western historiography in the 16th century, and in spite of the later Papal coronation of the Frankish Charlemagne as the Roman Emperor (25 December 800 CE) after the coronation of Empress Irene, whose claim, as a woman, was not recognized by Pope Leo III.

The title of all Emperors preceding Heraclius was officially "Augustus," although other titles such as "Dominus" were also used. Their names were preceded by "Imperator Caesar" and followed by "Augustus." Following Heraclius, the title commonly became the Greek "Basileus" (Gr. Βασιλεύς), which had formerly meant "sovereign" but was then used in place of 'Imperator. Following the establishment of the rival Holy Roman Empire in Western Europe, the title "Autokrator" (Gr. Αυτοκράτωρ) was increasingly used. In later centuries, the Emperor could be referred to by Western Christians as the "Emperor of the Greeks," though they still considered themselves "Roman" Emperors. Towards the end of the Empire, they referred to themselves as " in Christ, Emperor and Autocrat of the Romans."

On the medieval period, dynasties were common, but the principle of hereditary succession was never formalized in the Empire, and hereditary succession was a custom rather than an inviolable principle.