Ancient city of Bithynia in Asia Minor, modern Izmit, Turkey. From the 3rd to the 1st century b.c. it was the capital of Bithynia; later, the titular See of Bithynia Prima. Nicomedia was founded by King Zipoetes, whose son Nicomedes I made it his capital (c. 264 b.c.) and adorned it with numerous magnificent buildings. At the turn of the 2nd century B.C. Hannibal sought asylum at his court. Nicomedia remained the capital of Bithynia even after King Nicomedes III (or IV) willed the country to Rome (74 b.c.). pliny the younger in his letters to Trajan speaks of the senate house, an aqueduct that he had built, a forum, and the temple of Cybele. As capital of the province Nicomedia was one of the first cities in northern Asia Minor to be tianized. The first bishop of Nicomedia was Prochorus. Under Marcus Aurelius, Bp. dionysius of corinth wrote a letter to the faithful of Nicomedia (c. 170) warning them against the heresies of Marcion. Origen lived there with his benefactor, Ambrose (c. 240); and the emperor diocletian built there an imperial palace, a hippodrome, a mint, and an arsenal. constantine i was brought up there; the pagan philosopher Libanius taught there; and lactantius served as tutor to the children of the emperor. There was a Christian church close to the imperial palace, that was destroyed (303) when Diocletian initiated a severe persecution of the Christians of Asia Minor and hundreds were martyred. Under Maximinus Daia, in 312 the persecution in Nicomedia took the lives of many faithful members of the clergy, among them Bishop Anthimus and the priest Lucian of Antioch.
In the mid-4th century Bp. Eusebius of Nicomedia granted asylum to Arius, thus making the city a center of arianism. Two of its Arian bishops, Eudoxius and Demophilus, became archbishops of Constantinople. A Novatian sect settled in Nicomedia toward the end of the century. To the metropolitan See of Nicomedia (325) belonged the Dioceses of Chalcedon, Prusa, Apollonias, Hadrianoi, Caesarea in Bithynia, Nicaea, Chios, Neocaesarea, and Prusias; in the 7th century it was listed as seventh among the metropolitan sees of the Patriarchate of Constantinople.
During the 4th century Nicomedia suffered an invasion of the Goths and an earthquake (Aug. 24, 354), which ruined most of its buildings; fire completed the catastrophe. The city was rebuilt during the reign of justinian i (527–565), but subsequently was destroyed by the Shah Khusru (Chosroes) II. In 711 Pope Constantine I visited the city, and in 1073 John Comnenus was proclaimed emperor there. In about 1330 the sultan Orkhan captured the city and restored its ramparts, parts of which still display the two epochs of Nicomedia's history, the Roman and the Byzantine. Nicomedia continued to be a metropolitan see until 1923; since then it has been a Latin titular bishopric.
In a journey through Asia Minor in 1555, H. Dernschwam recognized walls and foundations of the ancient city, but could not identify them [Tagebuch einer Reise nach … Kleinasien, ed. F. Babinger (Munich 1923) 154–156, 238]. No systematic excavations had been attempted at Nicomedia by the late 20th century; however, some remains of buildings and inscriptions came to light in 1937. A contemporary portrait of Diocletian is of great interest.
Bibliography: b. kotter and o. feld, Lexikon für Theologie und Kirche, ed. j. hofer and k. rahner (Freiburg 1957–65) 7:1001–02. r. janin, Échos d'Orient 20 (Paris 1921) 168–182, 301–319; Dictionnaire d'histoire et de géographie ecclésiastiques, ed. a. baudrillart et al. (Paris 1912—) 9:20–28. v. schultze, Altchristliche Städte und Landschaften, (Gütersloh 1922) 2.1:244–305. h. leclercq, Dictionnaire d'archéologie chrétienne et de liturgie (Paris 1907–53) 12.1:1236–45. w. ruge, Paulys Realenzyklopädie der klassischen Altertumswissenschaft, ed. g. wissowa et. al, 17.1 (Stuttgart 1936) 468–492. f. k. dÖrner, Inschriften und Denkmäler aus Bithynien (Berlin 1941) 1–106, bibliog.