The Ghassanids, also known as the Jafnids, after their leaders, were allies of the Roman Empire for much of the sixth century. They played an important role as military auxiliaries, warding off attacks by the Arab allies of the Persian Sasanian Empire. Emerging in the sources in c. 500, they appear to have migrated from South Arabia and by the first quarter of the sixth century had assumed a position of leadership over Rome’s pre-existing network of Arab phylarchs (tribal leaders). The Jafnid leaders appear in literary, archaeological, and epigraphic sources as mediators in ecclesiastical disputes and benefactors of buildings and Christian cults. The final recognised Jafnid leader was toppled by the Roman Empire in c. 582, but they occupy a long afterlife in the Arab Islamic tradition, which provides many details not known from the Graeco-Roman and Syriac sources.