Poseidon is the God of the Sea and the brother of Zeus. He is second to power only to Zeus, and besides being ruler of the sea he gave the first horse to man. He is also known as "Earth Shaker", and he wields a mighty trident. He has the power to control the sea and weather, being able to produce thunderstorms. When the world was created, Zeus received the sky, Hades the underworld, and he the sea.

During the Trojan War he sided with the Greeks. He is the father of Otus and Ephialtes.