Nicomedes I, second king of Bithynia, was the eldest son of Zipoetes I, whom he succeeded on the throne in 278 BC.

Bithynia was an ancient region, kingdom and Roman province in the northwest of Asia Minor, adjoining the Sea of Marmara, the Bosporus, and the Black Sea. It bordered Mysia to the southwest, Paphlagonia to the northeast along the Pontic coast, and Phrygia to the southeast towards the interior of Asia Minor.