The Ghassanid kingdom was a Christian Arab kingdom that emigrated from Yemen to the Hauran, in south Syria. The Ghassanid emigration has been passed down in the rich oral tradition of southern syria. It is said that the Ghassanids came from the city of Ma'rib in Yemen. There was a dam in this Arabic city, however one year there was so much rain that the dam was carried away by the ensuing flood. Thus the people there had to leave. The inhabitants emigrated seeking to live in less arid lands and became scattered far and wide. The proverb "They were scattered like the people of Saba" refers to that exodus in history. The emigrants were from the southern arab tribe of Azd. The king A'mre, son of A'mer, emigrated with his family and retinue and many of his faithful followers north and settled in Hauran (south of damascus) where the Ghassanid state was founded. There it is assumed that the Arabs adopted the religion of Christianity from the native Aramaeans and Romans. Modern southern-syrians are a mix of these 3 peoples.

The Ghassanid kingdom was an ally of the Byzantine Empire. More accurately the kings should be described as phylarchs , native rulers of subject frontier states. The capital was at Jabiyah in the Golan Heights. Geographically, it occupied much of Syria, Palestine, Jordan and the northern Hijaz as far south as Yathrib (Medina). It acted as guardian of trade routes, policed Bedouin tribes and was a source of troops for the Byzantine army.The Ghassanid king al-Harith ibn Jabalah (reigned 529-569) supported the Byzantines against Sassanid Persia and was given the title patricius in 529 by the emperor Justinian. Al-Harith was a Monophysite Christian; he helped to revive the Syrian Monophysite (Jacobite) Church and supported Monophysite development despite Orthodox Byzantium regarding it as heretical. Later Byzantine mistrust and persecution of such religious unorthodoxy brought down his successors, al-Mundhir (reigned 569-582) and Nu'man.

The Ghassanids, who had successfully opposed the Persian allied Lakhmids of al-Hirah (Southern Iraq and Northern Arabia), prospered economically and engaged in much religious and public building; they also patronised the arts and at one time entertained the poets Nabighah adh-Dhubyani and Hassan ibn Thabit at their courts. Ghassan remained a Byzantine vassal state until its rulers were overthrown by the Muslims in the 7th century, following the Battle of Yarmuk. It was at this battle that some 12,000 Ghassanid Arabs defected to the Muslim side due to the Muslims offering to pay their arrears in wages. Their real power, however, had been destroyed by the Persian invasion in 614.