Athena's origin is one of the strangest in all Greek mythology. Her mother was Metis, the Titaness of cunning counsel, the first wife Zeus took when he became king of the Olympian gods. Gaia, the primordial Earth, and Ouranos, the Sky, had warned Zeus that Metis would bear him children, and that the first would be a daughter equal to her father in strength and counsel, but the second would be a son who would overthrow him just as Zeus had overthrown his own father Kronos. To prevent this fate, Zeus persuaded Metis to let him swallow her, and she, already pregnant with Athena, was consumed into his belly. There Metis forged her daughter's armor, the golden helmet, the spear, and the aegis, while Zeus suffered headaches so terrible that he cried out in agony. Finally Hephaestus, the lame smith-god who forged weapons for the Olympians, split Zeus's forehead open with an axe, and Athena leaped forth, fully grown, fully armed, and shouting a war-cry so mighty that Olympus itself reeled and the gods trembled. The Homeric Hymn to Athena describes the moment: the bright Son of Hyperion, Helios the Sun, stopped his swift-footed horses a long while, until the maiden had stripped the heavenly armor from her immortal shoulders and stood before her father, who was glad.

Her childhood was brief by divine standards, for she was born adult, but the myths that followed established her character with absolute clarity. She took the name Pallas after a playmate of the same name, the daughter of Triton, a sea-god who raised her in the marshes of Lake Tritonis. The two girls practiced war-games together, and one day Pallas was about to strike Athena when Zeus, watching from above, held his aegis before his daughter. Athena, startled, struck back and killed her friend accidentally. In grief, she carved an image of Pallas, the Palladium, and set it before Zeus as a memorial. In another version, she took the name after killing the Giant Pallas in the Gigantomachy, the war between the Olympian gods and the earth-born Giants who stormed heaven. Either way, the name marked her as both mourner and destroyer, a goddess who honored what she had killed. She remained forever a virgin, her heart inaccessible to love, and when Hephaestus, the smith-god, tried to force himself upon her, she repelled him so fiercely that his seed fell upon the earth and produced Erichthonius, the legendary first king of Athens, whom Athena raised in a chest and gave to the daughters of Cecrops, the serpent-king, with instructions never to open it. They did, and saw the child guarded by a serpent, and in terror they threw themselves from the Acropolis to their deaths.

The most famous contest of Athena's divine life was the rivalry with Poseidon for the patronage of Athens. The city was new, and the gods competed to become its protector. Poseidon, the god of earthquakes and the sea, struck the rock of the Acropolis with his trident and produced a salt spring, the Sea of Erechtheus, and then offered a horse, the animal of war. The Athenians were unimpressed; the water was brackish and undrinkable, and they had no need of more war. Athena struck the ground with her spear, and an olive tree sprouted instantly, its branches heavy with fruit, its oil useful for light, cooking, and anointing the body. King Cecrops, the serpent-man who was the first king of Athens, and the assembled Athenians chose the olive tree, and Athena became the patron goddess of the city that would bear her name forever. Poseidon was enraged, and he flooded the Thriasian Plain in western Attica, but the choice was made. The temple built to honor her, the Parthenon, was named for her epithet Parthenos, the Virgin, and every four years the Panathenaic Festival brought a procession from the city to the Acropolis, where a new peplos, a woven robe, was presented to her ancient wooden statue.

Athena's role in the great myths of heroes was equally defining. When Perseus, the son of Zeus and Danae, was sent by the tyrant Polydectes to fetch the head of the Gorgon Medusa, Athena gave him her polished bronze shield and instructed him to use it as a mirror, looking at Medusa's reflection rather than her face, which turned all living things to stone. She also guided his hand when he struck, and when the deed was done, Perseus gave her the Gorgon's severed head, which she fixed upon her aegis as the most terrible weapon in the divine arsenal. When Heracles, the hero forced to complete twelve impossible labors, was driven mad by Hera and killed his own wife and children, Athena was the one who stayed his hand before he could kill his father Amphitryon as well. She struck him unconscious with a stone, and when he woke, his madness had passed, leaving only the grief of what he had done. She accompanied him on several of his labors, including the capture of the horses of Diomedes and the retrieval of the golden apples of the Hesperides, and she was the one who finally welcomed him to Olympus after his death, reconciling him with Hera and securing his place among the gods.

But it was in the Trojan War and its aftermath that Athena showed the full range of her power. She sided with the Greeks against the Trojans, whom she had once favored, because the Trojan prince Paris had awarded the golden apple of discord to Aphrodite, the goddess of love, rather than to Athena or Hera, the queen of the gods. Paris had chosen beauty over wisdom and power, and Athena never forgave the insult. She fought beside the Greek warriors, protecting Diomedes when he wounded Ares, the god of bloodlust, and guiding the arrow that struck the heel of Achilles, the greatest Greek warrior, though some say that was Apollo's work. When the war ended and the Greek kings sailed for home, Athena's attention turned to Odysseus, the king of Ithaca, who had conceived the stratagem of the wooden horse that had finally breached Troy's walls. She favored him for his cunning, his patience, and his suffering, and when Poseidon, still furious over the blinding of his son the Cyclops Polyphemus, wrecked Odysseus's ships and scattered his crew, Athena intervened again and again. She appeared to his son Telemachus in the form of Mentor, an old friend of the family, and sent him to search for news of his father. She guided Odysseus through the land of the Phaeacians, where the princess Nausicaa found him naked and shipwrecked on the shore, and she finally restored him to his home after twenty years of absence, where he killed the suitors who had been consuming his wealth and pressing his wife Penelope to choose a new husband. Athena's last act in the Odyssey was to stop the feud that would have followed, commanding the Ithacans to swear peace and forget the blood that had been spilled.

Athena's wrath was as famous as her protection. When the weaver Arachne, a mortal woman of Lydia, boasted that her skill surpassed the goddess's own, Athena came to her in the guise of an old woman and warned her to repent. Arachne refused, and the goddess revealed herself and challenged the mortal to a contest. Athena wove a tapestry showing the gods in their majesty and the punishments of mortals who had dared to challenge them. Arachne wove a tapestry showing the gods in their disgrace, the secret loves and deceptions of Zeus and the other Olympians. The work was flawless, and Athena, unable to find fault with the weaving itself, tore the tapestry to pieces and struck Arachne with her shuttle. Arachne hanged herself in despair, but Athena took pity and transformed her into a spider, condemning her to weave forever. The transformation was both punishment and immortality, for Arachne's skill would never be forgotten. In another tale, the seer Teiresias accidentally saw Athena bathing on Mount Helicon, and she struck him blind, though his mother Chariclo begged for mercy. Athena could not undo the blindness, but she gave him the gift of prophecy and the staff by which he would feel his way through the world, turning a punishment into a kind of compensation that only a goddess of wisdom could devise.