Who Was Poseidon in Greek Mythology?

When the Titans were defeated, the three brothers divided the cosmos. Zeus took the sky, Hades took the underworld and Poseidon took the sea, with the land held in common between them.

That last detail matters. Poseidon's claim to the land was never settled, which is the source of several myths in which he competes with other gods for control of a city or region. He is a powerful god operating slightly outside his own domain, and it makes him restless.

Poseidon carried the title earth shaker, and the Greeks credited him with earthquakes. Living in a seismically active region, they connected the sea and the trembling ground as expressions of the same unpredictable power.

The link to horses is less obvious to modern readers. Poseidon was said to have created the first horse, and horses were associated with waves and with the sea's rolling motion. Sacrifices of horses into the sea are recorded in his worship.

The best known Poseidon story is his competition with Athena for the patronage of a new city. Poseidon struck the ground with his trident and produced a spring of salt water. Athena produced an olive tree.

The people judged the olive more useful and the city became Athens. Poseidon reacted badly, and in some versions flooded the plain in anger. This pattern repeats: Poseidon competes, loses and retaliates, which is a good summary of how the Greeks saw the sea.

Poseidon drives much of the plot of the Odyssey. Odysseus blinds the cyclops Polyphemus, who is Poseidon's son, and the god spends the next ten years preventing him from reaching home.

The story is a useful window into Greek attitudes. For a seafaring people, the sea was essential and lethal, and its temperament could not be predicted or reasoned with. A god who holds a grudge for a decade over an insult to his son captures that relationship precisely.

Poseidon received serious attention from anyone whose life depended on water:

• •Sailors making offerings before voyages and after safe returns
• •Coastal cities building temples on prominent headlands
• •Horse breeders and cavalry honouring him
• •Communities in earthquake prone regions seeking protection

One of Poseidon's more consequential interventions began with a gift. He sent King Minos of Crete a magnificent white bull as a sign of divine favour, expecting it to be sacrificed back to him.

Minos kept the bull and sacrificed a lesser one instead. Poseidon's revenge was indirect and devastating: he caused Minos's wife to fall in love with the bull, and the child of that union was the Minotaur. The labyrinth, Theseus, Daedalus and Icarus all follow from a single withheld sacrifice, which shows how tightly Greek myths interlock.

Poseidon is one of the oldest Greek gods that historians can actually document. Clay tablets written in Linear B, an early script used to write Greek in the Mycenaean palaces of the late Bronze Age, include his name among the gods receiving offerings. At the palace of Pylos in the south-western Peloponnese, he appears to have been especially important, receiving substantial gifts. This evidence comes from centuries before Homer, and it suggests that Poseidon was already a major figure long before the familiar myths were written down in their classical forms.

Later Greek worship left visible monuments. The marble temple at Cape Sounion, built in the fifth century BCE on a cliff at the southern tip of Attica, would have been one of the first things sailors saw as they approached Athens. The Isthmian Games, held near Corinth every two years, were dedicated to Poseidon and ranked among the major athletic festivals of the Greek world. When the Romans later identified their own water god Neptune with Poseidon, they absorbed many of these stories along with him.

Poseidon's role in the Trojan War has a backstory. According to myth, he and Apollo once served King Laomedon of Troy for a year, and Poseidon built the city's great walls. When the work was done, Laomedon refused to pay the agreed wages. Poseidon sent a sea monster to attack the city, and Laomedon's daughter Hesione was offered to it, until Heracles killed the creature, only to be cheated by the king as well. In the Iliad, Poseidon generally supports the Greeks against the Trojans, and the old grievance helps explain why.

Poseidon also has a central place in one of the most famous invented stories of antiquity. In his dialogues Timaeus and Critias, the philosopher Plato describes Atlantis, a powerful island empire said to have sunk beneath the sea. In Plato's account, Atlantis was Poseidon's share when the gods divided the earth, and the god fathered its first kings, the eldest named Atlas, who gave his name to the island and the ocean. Most scholars read Atlantis as a story Plato created to explore ideas about the ideal state and the dangers of pride, not as a record of a real place.

In Greek art Poseidon usually looks very much like his brother Zeus: a mature, bearded, powerful man. The surest way to tell them apart is what he holds. Poseidon carries the trident, a three-pronged spear resembling the tools Mediterranean fishermen used to spear large fish such as tuna, while Zeus usually holds a thunderbolt or a sceptre. Poseidon may also appear with dolphins, fish or horses, or riding a chariot over the waves beside his wife, the sea goddess Amphitrite. On painted pottery, where many gods share the same build and beard, these attributes are often the only reliable label.

When the attribute is missing, experts can disagree. A famous example is the Artemision Bronze, a larger than life statue of a naked bearded god recovered in the twentieth century from an ancient shipwreck off Cape Artemision and now displayed in the National Archaeological Museum in Athens. The god stands with one arm stretched forward and the other drawn back to throw something, but the object itself is lost. A thunderbolt would make him Zeus, and a trident would make him Poseidon. Many scholars favour Zeus, partly because a long trident would cross in front of the face from some angles, but the question remains open.

Many of Poseidon's children share his wild, unpredictable nature. Besides the cyclops Polyphemus, he was said to have fathered the giant Antaeus, who drew strength from touching the earth until Heracles lifted him off the ground and crushed him. In the best known version of the Medusa story, Poseidon was the father of the winged horse Pegasus, who sprang from her neck when Perseus beheaded her, which fits the god's link with horses. With his wife Amphitrite he had Triton, a merman often shown blowing a conch shell to calm or raise the waves.

Theseus, the great Athenian hero, was credited with two fathers, the mortal king Aegeus and Poseidon. A poem by Bacchylides tells how, on the voyage to Crete, King Minos threw a gold ring into the sea and dared Theseus to prove his divine birth by fetching it. Theseus dived, was carried to the god's undersea palace and returned with gifts from Amphitrite. The connection had a darker side. In Euripides' play Hippolytus, Theseus wrongly believes his son guilty and calls on a curse promised by Poseidon, and a bull from the sea panics the young man's horses, killing him.

Poseidon in Greek mythology ruled the sea while also governing earthquakes and horses, and his repeated pattern of competing, losing and taking revenge reflected exactly how a seafaring people experienced the ocean.