Only the emperors who were recognized as legitimate rulers and exercised sovereign authority are included, to the exclusion of junior co-emperors (symbasileis) who never attained the status of sole or senior ruler, as well as of the various usurpers or rebels who claimed the imperial title.

Emperors listed below up to Theodosius I in 395 were sole or joint rulers of the entire Roman Empire.

Following the establishment of the rival Holy Roman Empire in Western Europe, the title "Autokrator" (Gr.

[3] Dynasties were a common tradition and structure for rulers and government systems in the Medieval period.

The principle or formal requirement for hereditary succession was not a part of the Empire's governance;[4] hereditary succession was a custom and tradition, carried on as habit and benefited from some sense of legitimacy, but not as a "rule" or inviolable requirement for office at the time.