Bithynia, an ancient country of northwestern Asia Minor, now part of Turkey. In early times the region was settled by people from Thrace in the eastern Balkan Peninsula. About 560 B.C., King Croesus of Lydia conquered Bithynia. In 546 Croesus in turn was defeated and captured by Cyrus the Great. The region then was part of the Persian Empire until 334 B.C., when it fell to Alexander the Great.
After Alexander's death, Bithynia gained independence and developed into a flourishing kingdom. In 74 B.C., it came under the control of Rome and became a Roman province. When the Roman Empire was divided in 395 A.D., Bithynia became part of the Eastern, or Byzantine, Empire. The Seljuks conquered the region in the 11th century. Two centuries later Bithynia fell to the Ottoman Turks.