Rhesaena (Rhesaina) is a Catholic titular see. The original diocese was in Osrhoene, a suffragan of Edessa.
Rhesaena (Resaena: numerous variations of the name appear in ancient authors) was an important town at the northern extremity of Mesopotamia, near the sources of the Chaboras (now the Khabur River. It was on the way from Carrhæ to Nicephorium, about eighty miles from Nisibis and forty from Dara. Nearby, Gordian III fought the Persians in 243, at the battle of Resaena. It is now Ra's al-'Ayn, Syria.
Its coins show that it was a Roman colony from the time of Septimus Severus. The Notitia dignitatum (ed. Boecking, I, 400) represents it as under the jurisdiction of the governor or Dux of Osrhoene. Hierocles (Synecdemus, 714, 3) also locates it in this province but under the name of Theodosiopolis; it had in fact obtained the favour of Theodosius the Great and taken his name. It was fortified by Justinian. In 1393 it was nearly destroyed by Tamerlane's troops.
Read more about Rhesaena: Bishops