in Greek mythology, a king of Iolcus in Thessaly who imposed on his half-nephew Jason the task of bearing off the Golden Fleece. According to Homer, Pelias and Neleus were twin sons of Tyro (daughter of Salmoneus, founder of Salmonia in Elis) by the sea god Poseidon, who came to her disguised as the river god Enipeus, whom she loved. The twins were exposed at birth but were found and raised by a horse herder. Later, Pelias seized the throne and exiled Neleus, who became king in Pylos.

Later legend relates that on Jason's return with the fleece, his wife Medea, the enchantress, took revenge on Pelias by persuading his daughters, except for Alcestis, to cut up and boil their father in the mistaken belief that he would thereby recover his youth.