Constantia or Konstantia (Ancient Greek: Κωνσταντία) was a town of some importance in the province Osrhoene in Mesopotamia, on the road between Nisibis and Carrhae, at no great distance from Edessa. It was, after his departure from Nisibis, the residence of the dux Mesopotamiae until the foundation of Dara. There is considerable variation in different authors in the way in which the name of this town is written and the names under which it is known, including: Constantia or Konstantia (Κωνσταντία), Constantina or Konstantina (Κωνσταντίνα), Antoninopolis, Nicephorium or Nikephorion (Νικηφόριον), Maximianopolis (Μαξιμιανούπολις), Constantinopolis in Osrhoene, Tella and Antiochia Arabis, Antiochia in Mesopotamia (Ἀντιόχεια τῆς Μεσοποταμίας – Antiocheia tes Mesopotamias) and Antiochia in Arabia (Ἀντιόχεια ἡ Ἀραβική – Antiocheia e Arabike).
According to Pliny it was founded by Seleucus I Nicator after the death of Alexander the Great. According to the Byzantine historian John Malalas, the city was built by the Roman Emperor Constantine I on the site of former Maximianopolis, which had been destroyed by a Persian attack and an earthquake. Jacob Baradaeus was born near the city and was a monk in a nearby monastery.
Under the names Constantina and Tella, it was also a bishopric, suffragan of Edessa; some names of early bishops have been preserved, including Sophronius who attended the Council of Antioch in 445. No longer a residential bishop, it remains a titular see of the Roman Catholic Church under the name Constantina. The city was captured by the Arabs in 639.
- Procopius, de Aed 2.5.
- Hierocles. Synecdemus. p. 714.
- Suda, s.v.
- Smith, William, ed. (1854–1857). "Constantia". Dictionary of Greek and Roman Geography. London: John Murray.
- Stephanus of Byzantium. Ethnica. s.v.
- under which name the bishop who attended the Council of Chalcedon is titled; Evagrius Scholasticus, H.E. i; Smith, William, ed. (1854–1857). "Constantia". Dictionary of Greek and Roman Geography. London: John Murray.
- Richard Talbert, ed. (2000). Barrington Atlas of the Greek and Roman World. Princeton University Press. p. 89, and directory notes accompanying.
- Pliny. Naturalis Historia. 6.117.
- Malala, Chron. xii. p. 312.
- Kazhdan, Alexander, ed. (1991), Oxford Dictionary of Byzantium, Oxford University Press, p. 497, ISBN 978-0-19-504652-6
- Lund University. Digital Atlas of the Roman Empire.