Bithynia, an ancient country of Asia Minor, bounded N. by the Euxine, E. by Paphla-gonia, S. by Phrygia and Galatia, and W. by the Propontis and Mysia, and comprising the N. E. portions of the Turkish eyalet of Kho-davendigiar. According to Herodotus, the Bi-thyni came from the banks of the Strymon in Thrace, having been expelled thence by a more powerful horde; and Thucydides and Xenophon corroborate this statement by calling their descendants Bithynian Thracians. The Bithynians maintained their independence till they were subdued by Croesus, king of Lydia. On the overthrow of the Lydian monarchy they passed under the power of the Persians, and their country became a part of the satrapy of Phrygia. In later times, however, it was itself constituted into a satrapy, and even a native dynasty sprang up in it. After the defeat of the Persians on the Granicus, Bithy-nia fell under the sway of the Macedonians. On the death of Alexander the Great, Bas, the son of Botiras, a native chief, vanquished Calantus, the Macedonian governor, and took possession of Bithynia for himself and his posterity. Nicomedes, the fourth in descent from Botiras, was the first of this dynasty who assumed the title of king. The kingdom of Bithynia endured for over two centuries.
Its last king was Nicomedes III., who, having no children, bequeathed his dominions to the Romans, 74 B. C. The Romans annexed Bithynia first to the province of Asia, and then to that of Pontus. In the reign of Augustus it was separated from the latter, and, together with the western part of Paphlagonia, constituted a proconsular province. The inland districts of Bithynia were mountainous and woody, embracing the Bithynian Olympus; but the country near the coast consisted for the most part of fertile plains, which were studded with villages. Its chief river was the Sanga-rius (now Sakaria), which traversed it from south to north. Among its towns were Nico-media'and Prusa (Brusa), successively capitals, Heraclea, Chalcedon, and Nicaea.