The city was founded by the Nabataeans as Suada. It became known as Dionysias (Greek: Διονύσιας) in the Hellenistic and Roman times, for Dionysus the god of wine - the city is situated in a famous ancient wine-producing region.
The name Dionysias replaced the former Nabatean name of Suada in 149 AD after the Nabataean influence decreased and then concentrated towards the south, as a result of the accelerating Hellenization of Coele-Syria at that time.
Dionysias was a part of the Roman province of Arabia Petraea, and received the rights of civitas under the reign of Commodus between 180–185.
Dionysus was worshipped in the same Nabatean temple dedicated for Dushara. This practice of associating the worship of local and Hellenic gods was common in Hellenistic Syria.
This name remained in use during the Byzantine period, when the town was under the influence of Ghassanids, Dionysias then was a Diocese as a suffragan of Bosra. It was mentioned in the Synecdemus of Hierocles. After the Arab conquests it became a titular see.
Yaqut al-Hamawi noted in the 1220s that As Suwaida was "a village of the Hauran Province".
In recent times Dionysias was firstly identified as Sweida by William Henry Waddington
