According to traditional historians, the Ghassanids were part of the al-Azd tribe, and they emigrated from South Arabia, modern day Yemen.
They traveled across the Arabian Peninsula and eventually settled in the Roman limes.
The tradition of Ghassanid migration finds support in the Geography of Claudius Ptolemy, which locates a tribe called the Kassanitai south of the Kinaidokolpitai and the river Baitios (probably the wādī Baysh).
These are probably the people called Casani in Pliny the Elder, Gasandoi in Diodorus Siculus and Kasandreis in Photios (relying on older sources).

The date of the migration to the Levant is unclear, but they are believed to have arrived in the region of Syria between 250-300 AD and later waves of migration circa 400 AD.
Their earliest appearance in records is dated to 473 AD, when their chief Amorkesos signed a treaty with the Eastern Roman Empire acknowledging their status as foederati controlling parts of Palestine.
 He apparently became Chalcedonian at this time.
By the year 510, the Ghassanids were no longer Miaphysite, but Chalcedonian.
They became the leading tribe among the Arab foederati, such as Banu Amela and Banu Judham.
According to traditional historians, the Ghassanids were part of the al-Azd tribe, and they emigrated from South Arabia, modern day Yemen. They traveled across the Arabian Peninsula and eventually settled in the Roman limes. The tradition of Ghassanid migration finds support in the Geography of Claudius Ptolemy, which locates a tribe called the Kassanitai south of the Kinaidokolpitai and the river Baitios (probably the wādī Baysh). These are probably the people called Casani in Pliny the Elder, Gasandoi in Diodorus Siculus and Kasandreis in Photios (relying on older sources).
The date of the migration to the Levant is unclear, but they are believed to have arrived in the region of Syria between 250-300 AD and later waves of migration circa 400 AD. Their earliest appearance in records is dated to 473 AD, when their chief Amorkesos signed a treaty with the Eastern Roman Empire acknowledging their status as foederati controlling parts of Palestine.  He apparently became Chalcedonian at this time. By the year 510, the Ghassanids were no longer Miaphysite, but Chalcedonian. They became the leading tribe among the Arab foederati, such as Banu Amela and Banu Judham.
Ghassanids