(Greek mythology) The god of the sea and earthquakes in ancient mythology; brother of Zeus and Hades and Hera; identified with Roman Neptune.
In Greek mythology, the chief god of the sea (Roman Neptune), brother of Zeus and Pluto. The brothers dethroned their father, Cronus, and divided his realm, Poseidon taking the sea; he was also worshiped as god of earthquakes. His sons were the merman sea god Triton and the Cyclops Polyphemus.