Nauplius was a demigod and a son of Poseidon and Amymone.
Nauplius was the son of the god Poseidon and Amymone, daughter of Danaus. He reputedly founded Nauplia, of which the inhabitants Pausanias believed were descendants of the Egyptians who had once arrived with Danaus to Argolis. He was renowned as an expert seafarer, and possibly the inventor of seafaring as a practice; a harbor equipped by him to function as a port was said to have been named in his honor. According to Pherecydes, he was father of Damastor, through him grandfather of Peristhenes and great-grandfather of Dictys and Polydectes.