Paphlagonia (; ) was an ancient area on the Black Sea coast of north central Anatolia, situated between Bithynia to the west and Pontus to the east, and separated from Phrygia (later, Galatia) by a prolongation to the east of the Bithynian Olympus. According to Strabo, the river Parthenius formed the western limit of the region, and it was bounded on the east by the Halys river.