Poseidon, in the Greek mythology the god of the sea, a son of Kronos and Rhea, and brother of Zeus, Pluto, Hera, Hestia, and Demeter; had his home in the sea depths, on the surface of which he appeared with a long beard, seated in a chariot drawn by brazen-hoofed horses with golden manes, and wielding a trident, which was the symbol of his power, exercised in production of earthquake and storms. See Pluto.