The Ghassanids (الغساسنة, also Banu Ghassān (بنوغسان, romanized as: ; Ghassanidae; Γασσανίδες, Gassanídes), also called the Jafnids, were an Arab tribe which founded a kingdom. They emigrated from South Arabia in the early third century to the Levant. Some merged with Hellenized Christian communities, converting to Christianity in the first few centuries, while others may have already been Christians before emigrating north to escape religious persecution.
After settling in the Levant, the Ghassanids became a client state to the Byzantine Empire and fought alongside them against the Sasanian Empire and their Arab vassals, the Lakhmids. The lands of the Ghassanids also acted as a buffer zone protecting lands that had been annexed by the Romans against raids by Bedouins.
Few Ghassanids became Muslims following the Muslim conquest of the Levant; most Ghassanids remained Christian and joined Melkite and Syriac communities within what is now Jordan, Israel, Palestine, Syria and Lebanon.
In the Arab genealogical tradition which developed during the early Islamic period, the Ghassanids were considered a branch of the Azd tribe of South Arabia/Yemen. In this genealogical scheme, their ancestor was Jafna, a son of Amr Muzayqiya ibn Mazin ibn Azd, through whom the Ghassanids were purportedly linked with the Ansar (the Aws and Khazraj tribes of Medina), who were the descendants of Jafna's brother Tha'laba. According to the historian Brian Ulrich, the links between Ghassan, the Ansar, and the wider Azd are historically tenuous, as these groups are almost always counted separately from each other in sources other than post-8th-century genealogical works and the story of the 'Scattering of Azd'. In the latter story, the Azd migrate northward from Yemen and different groups of the tribe split off in different directions, with the Ghassan being one such group.
Per the "Scattering of Azd" story, the Ghassanids eventually settled within the Roman limes.