The third son of Kronos and the brother of Zeus and Hades, he drew the seas as his domain to rule. He was known also as the god of earthquakes and the god of horses. The symbols most often associated with Poseidon were the trident and dolphin. Sailors relied upon him for favorable winds and safe voyages, but he was moody. Despite sacrifices including drowned horses, he could cause storms, bad winds, and earthquakes at a whim. Like Zeus, he projected his power and masculinity on women, fathering many children. 

In a famous contest between himself and Athena to decide which of the two would be the patron god of Athens, he threw a spear into the ground to create the Spring of the Acropolis. Athena surpassed him, however, by creating the olive tree. He often used water and earthquakes to exact revenge, but could be cooperative as well. He greatly aided the Greeks in the Trojan War, but took years of revenge on Odysseus, who had harmed one of Poseidon's Cyclops offspring.