Bartın River (Bartın Çayı), anciently known as Parthenius or Parthenios (Ancient Greek: Παρθένιος), is a small river in the east of the Black Sea Region of Turkey. Its source is in the Ilgaz Mountains, in Kastamonu Province and Karabük Province. The river flows to the north, passes through Bartın, and empties into the Black Sea near Boğaz village in a delta.
The last 14 kilometres (9 mi) on the Bartın River, between Bartın and the Black Sea coast, are navigable for vessels.
Paphlagonia (/ˌpæfləˈɡoʊniə/; Greek: Παφλαγονία, romanized: Paphlagonía, modern translit. Paflagonía; Turkish: Paflagonya) was an ancient region 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 region was bounded by the river Parthenius to the west and the Halys River to the east. Paphlagonia was said to be named after Paphlagon, a son of the mythical Phineus.