Wikipedia
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. The name Paphlagonia is derived in the legends from Paphlagon, a son of Phineus. (Eustath. ad Horn. II. ii. 851, ad Dion. Per. 787; Steph. B. t.v.; Const. Porph. de Them. i. 7.)
The Theme of Paphlagonia was a military-civilian province (thema or theme) of the Byzantine Empire in the namesake region along the northern coast of Anatolia, in modern Turkey.