Nicomedes IV Philopator was the king of Bithynia from c. 94 BC to 74 BC. He was the first son and successor of Nicomedes III of Bithynia.

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.