In the Eastern Roman Empire (395–1453), rebellion and usurpation were so notoriously frequent (in the vision of the medieval West, where usurpation was rare) that the modern term "byzantine" became a byword for political intrigue and conspiracy.
The following individuals began as usurpers, but became the legitimate emperor either by establishing uncontested control of the empire or by confirmation of their position by the Roman Senate or by the legitimate emperor.
[1] Three of them, (Constantine III, Priscus Attalus, and Constans II), reigned alongside the legitimate Emperor of the West Honorius, who accepted Constantine III as his co-emperor in 409.
Upon his recognition, Constantine III appointed his son Constans II co-emperor.
They are listed here under the emperor whose rule they attempted to usurp.