Nicomedes I, the son of Zipoete, became the king of Bithynia (c. 278 - c. 248 BC) on the death of his father.
He made himself master of the whole country and put to death his brother, who had set himself up as an independent ruler. He enlarged and consolidated the kingdom, founded the great city of Nicomedia as the capital, and fought successfully for some time with Antiochus I Soter of Syria. He invited the Gauls across the Bosporus to help him in his battles, and helped them to settle in Phrygia.
His reign seems to have been prosperous and uneventful; the year of his death is uncertain.