Neleus was the son of Poseidon and Tyro in Greek mythology, and twin brother of Pelias. Tyro was the wife of Cretheus, but was secretely in love with the river god Enipeus. However, Enipeus rejected her. Poseidon, having fallen for Tyro, took the form of Enipeus and seduced Tyro; after sleeping together, Tyro became pregnant and gave birth to the twin brothers, Neleus and Pelias. Tyro abandoned the two babies on a mountain to die, but a maid found them and raised them.
When Neleus and Pelias reached adulthood, they sought their mother, who at the time was being mistreated by their stepmother, Sidero. Sidero tried to evade them by hiding into a temple of Hera, but Pelias found her and killed her anyway; this is how he received the hatred of the goddess. The two brothers then fought for the throne, and Neleus lost; he was banished to Messenia, where he became the king of Pylos. He married Chloris, with whom he had four children; Pero, Periclymenus, Alastor, and Nestor. At a later time, Heracles asked Neleus to release him from a blood-debt; after being refused, Heracles killed Neleus and his sons except Nestor.