Leo III the Isaurian, also known as the Syrian, was Byzantine Emperor from 717 until his death in 741 and founder of the Isaurian dynasty. He put an end to the Twenty Years' Anarchy, a period of great instability in the Byzantine Empire between 695 and 717, along with bringing an end to the continual defeats and territorial losses the Byzantines had suffered during the seventh century, marked by the rapid succession of several emperors to the throne. He also successfully defended the Empire against the invading Umayyads and forbade the veneration of icons.

The Byzantine Empire was ruled by the Isaurian dynasty from 717 to 802. The Isaurian emperors were successful in defending and consolidating the empire against the caliphates after the onslaught of the early Muslim conquests, but were less successful in Europe, where they suffered setbacks against the Bulgars, had to give up the Exarchate of Ravenna, and lost influence over Italy and the papacy to the growing power of the Franks.