Bithynia is a territory in northwestern Asia Minor across the Propontis from Constantinople. It was a kingdom, a Persian satrapy and later a Roman province.
In 75/4 B.C. King Nicomedes IV, particularly noteworthy for his alleged sexual association with Julius Caesar, bequeathed Bithynia to Rome in return for Rome's help against the king of Pontus. After Rome defeated Mithridates VI of Pontus, Rome combined Bithynia and Pontus into a single province of which Pliny the Younger became governor (109/110-111/112) under Trajan. Bithynia only became a separate province in the fourth century.
Bithynia's capital city was Nicomedia, where the tetrarchy Emperor Diocletian was stationed. Diocletian's successors stayed there until about 330 when Emperor Constantine founded the eastern capital Constantinople. Other important cities in Bithynia were Nicaea (home of the Nicene Council from which came the Nicene Creed) and Chalcedon (another city important in early Christianity).
- Clive F. W. Foss "Bithynia" The Oxford Dictionary of Byzantium. Ed. Alexander P. Kazhdan. Oxford University Press 1991.
- "Bithynia" Oxford Dictionary of the Classical World. Ed. John Roberts. Oxford University Press, 2007.