Paphlagonia, in ancient geography, a country in the north of Asia Minor, bounded N. by the Euxine sea, E. by Pontus, from which it was separated by the river Halys (the modern Kizil Irmak), S. by Galatia, and W. by Bithynia. The chief city was Sinope, founded by a Greek colony, on the Euxine; and other important places were Cytorus and Amastris on the coast, and Pompeiopolis and Gangra in the interior. The only important rivers, besides the Halys, were the Amnias (Kara-su), its tributary, and the Parthenius (Bartan-su), on the Bithynian border. The Olgassys mountains (Ilkaz Dagh) in the centre, an extension of the chain running from Armenia to the Hellespont, send up to the northern part of the country numerous branches.. Generally the surface is mountainous and rugged, especially in the southern portion, the northern containing many wide and fertile valleys. Paphlagonia was celebrated for its horses, and also produced mules and antelopes, and in some parts sheep breeding was common, while the vast forests in the south afforded an ample supply of timber. A kind of red ochre was obtained in the neighborhood of Pompeiopolis. The Paphlagonians appear to have been a Syrian race, and were rude and superstitious.

The chase was a favorite pursuit in peace, and their cavalry was celebrated in war. - Paphlagonia was originally governed by native princes, but was annexed to Lydia by Croesus; and after the conquest of that kingdom by Cyrus, it formed a portion of the third satrapy of the Persian empire, though various satraps made themselves independent rulers. After the death of Alexander, Paphlagonia fell into the hands of Eumenes; but after his fall it was again independent until it became a part of the dominions of Mithri-dates, king of Pontus. The Romans united the coast districts with Bithynia, and subsequently incorporated the whole country with the province of Galatia; but Constantine erected it into a separate province. It is now embraced in the Turkish vilayet of Kastamuni.