Aegeus, one of the primordial kings of Athens, was childless and sought counsel from the Oracle of Delphi. The oracle gave him cryptic guidance: not to loosen the bulging mouth of the wineskin until he had reached the height of Athens, lest he die of grief. Unable to understand it, Aegeus consulted his host Pittheus, king of Troezen, who grasped the prophecy's meaning. Pittheus made Aegeus drunk and gave him his daughter Aethra.

Following Athena's instructions in a dream, Aethra left the sleeping Aegeus and waded to the nearby island of Sphairia, where she poured libations to Sphairos and Poseidon, and the sea god lay with her that night. This divine-and-mortal coupling gave Theseus the characteristics of both immortal and human nature, a familiar pattern among Greek heroes; he is thus said to have had two fathers, Aegeus and Poseidon.

After Aethra became pregnant, Aegeus decided to return to Athens. Before departing he buried his sandals and sword beneath a great rock and instructed Aethra that, when their son matured and proved heroic enough to move the rock, he should retrieve these tokens as proof of his royal parentage. Meanwhile, in Athens, the sorceress Medea, who had fled Corinth after killing her children with Jason, became Aegeus's consort.

Theseus grew up in his mother's homeland. On reaching manhood he successfully moved the rock and recovered his father's tokens. His mother then revealed his paternity and instructed him to carry the sword and sandals to King Aegeus to claim his inheritance. Theseus faced a choice: travel safely by sea, or take the perilous overland route around the Saronic Gulf, where six entrances to the Underworld awaited, each guarded by a dangerous enemy. The young, ambitious hero chose the dangerous path and defeated numerous bandits along the way.

The six entrances to the Underworld along the road, commonly known as Theseus's Six Labours, presented formidable challenges.

At Epidaurus, sacred to Apollo and the healer Asclepius, Theseus confronted Periphetes, the "Club Bearer," a bandit who beat his opponents into the earth. Theseus defeated him and claimed the stout club that would become his signature weapon in vase-paintings.

At the Isthmus of Corinth lived Sinis, nicknamed "Pityokamptes" (he who bends pine trees). This robber bound travellers between two pines bent to the ground, then released the trees, tearing his victims apart. Theseus used Sinis's own method against him, then lay with his daughter Perigune, fathering the child Melanippus.

North of the Isthmus, near Crommyon, Theseus killed an enormous pig called the Crommyonian Sow, bred by an old crone named Phaea (in some accounts Phaea is the sow itself). The Bibliotheca describes this creature as offspring of the monsters Typhon and Echidna.

Near Megara, the robber Sciron forced travellers along a narrow cliff path to wash his feet. As they knelt he would kick them off the cliff, where a giant turtle (or sea monster in some versions) devoured them. Theseus pushed Sciron off the same cliff to the same fate.

Cercyon, king of the holy site of Eleusis, challenged all passers-by to wrestling matches and, upon defeating them, killed them. Theseus bested him in wrestling and killed him in return.

The final bandit was Procrustes the Stretcher, who possessed two beds of different lengths. He forced travellers to lie in one, then either stretched them or cut off their feet to make them fit, so that none could survive. Theseus subjected him to his own method, cutting him to fit and decapitating him.

On arriving in Athens, Theseus initially concealed his true identity. King Aegeus received him hospitably but viewed the powerful young stranger with suspicion. Medea, however, recognised Theseus at once as Aegeus's son. Fearing that he would be chosen as heir over her own son Medus, she plotted his death by persuading Aegeus to send him to capture the Marathonian Bull, an emblem of Cretan power.

On his way to Marathon, Theseus sheltered during a storm in the hut of an elderly woman named Hecale, who vowed to sacrifice to Zeus if Theseus succeeded. Theseus captured the bull, but on returning to Hecale's dwelling found her dead. In her honour he named one of Attica's demes after her, making its inhabitants her adopted children.

When Theseus returned victorious to Athens and sacrificed the bull, Medea attempted to poison him. At the crucial moment Aegeus recognised the sword and sandals and knocked the poisoned cup from Theseus's hands. Father and son were thus reunited, and Medea fled to Asia.

Theseus's reputation had spread through Athens because of his journey along the notorious coastal road and his defeat of feared bandits. The Pallantides, the sons of Pallas and nephews of the childless King Aegeus, realised their hopes of succession would vanish if Theseus lived. They laid a trap, planning to march on the town from one direction while another group ambushed from Gargettus, forcing Theseus and Aegeus out through the front to be taken from behind. But a herald named Leos warned Theseus of the scheme. He crept out at midnight, attacked the ambush party and slew them all; when the Pallantides learned of this, their force scattered in disarray.

Androgeus, eldest son of King Minos of Crete, sailed to Athens to compete in the Panathenaic Games. Being strong and skilful he won many events and became a crowd favourite, breeding resentment among the Pallantides, who assassinated him and so incurred Minos's terrible wrath.

When Minos learned of his son's death he sent the Cretan fleet against Athens and demanded that Aegeus surrender the assassins or face destruction. Unable to identify them, the king surrendered the city to Minos's mercy. The retribution was harsh: as tribute, courageous youths and beautiful maidens were to be sent to Crete, never to return. In another version Minos had conquered Athens in war and demanded that every nine years seven Athenian boys and seven girls be sent to the island to be devoured by the Minotaur, a half-man, half-bull monster dwelling in a Labyrinth built by Daedalus.

On the third occasion of this tribute, Theseus volunteered to stop the monster. He joined the sacrificial youths, sailing under a black sail and promising his father Aegeus that he would return under a white sail if successful. Like the others, Theseus was stripped of his weapons on arrival in Crete.

Minos's daughter Ariadne fell in love with Theseus on sight. Following Daedalus's advice, she gave him a ball of thread so he could find his way back through the Labyrinth. That night she led him to the entrance, and Theseus swore that if he survived he would take her with him. Before entering he tied one end of the thread to the doorpost and kept a sword hidden inside his tunic.

Following Daedalus's instructions, to go forward and down and never turn left or right, Theseus reached the heart of the Labyrinth and found the sleeping Minotaur. The beast awoke and a tremendous struggle ensued; Theseus overpowered it and stabbed it in the throat with his sword (one ancient source says he strangled it). After killing the beast, he used the thread to escape the Labyrinth.

Theseus fled with all the young Athenians, with Ariadne and with her younger sister Phaedra. The group fell asleep on the beach of the island of Naxos, and there Theseus abandoned Ariadne; Dionysus later found and married her. During the voyage home he stopped at Delos, where, according to Plutarch, he danced with the young Athenians a dance imitating the twisting passages of the labyrinth, called the Crane.

Tragically, Theseus forgot to raise the white sails as promised. His father, believing his son dead, threw himself from a cliff at Sounion into the sea below, which thereafter became known as the Aegean Sea.

According to Plutarch, the ship in which Theseus returned from Crete to Athens was preserved in the Athenian harbour as a memorial for several centuries. As the timber aged and decayed, the Athenians replaced the old planks with new, stronger ones, keeping the vessel seaworthy.

The ship had to remain functional because Athens had pledged to honour Apollo each year in return for Theseus's successful mission. The Athenians sent a sacred delegation to Delos aboard this very galley, and to preserve the mission's purity no executions were permitted from the moment the ceremony began until the ship returned, a journey lasting several weeks.

Because any rotting wood was replaced over time, a philosophical puzzle arose: once all the original planks had been replaced, could the ship still be considered the same ship? This question about the nature of identity became known as the "Ship of Theseus" paradox. Despite it, the Athenians continued to preserve the vessel, believing Theseus had been an actual historical figure and that the ship gave them a tangible link to their ancestry.

Theseus's closest companion was Pirithous, king of the Lapiths. Having heard of Theseus's courage and strength, Pirithous wished to test it and rustled his cattle from Marathon. Theseus pursued him, and both took up arms to fight; but on meeting, each was so impressed by the other's beauty, grace and courage that they swore a solemn oath of friendship and joined together in the Calydonian boar hunt. In Homer's Iliad, the aged Nestor recalls Pirithous and Theseus as the strongest men of an earlier generation, who utterly destroyed a savage mountain-dwelling tribe.

Later, when Pirithous married Hippodamia, the centaurs invited to the wedding became drunk and tried to abduct the women, including the bride. The Lapiths defeated them in the ensuing battle, and according to Ovid, Theseus himself killed Eurytus, the fiercest of the centaurs. Ovid also notes that Phaedra grew jealous of her husband's devotion to Pirithous, using this as justification for her attempt to seduce Hippolytus.

Since both men claimed descent from Zeus, Theseus and Pirithous pledged to marry daughters of Zeus. Theseus chose Helen and they kidnapped her, intending to keep her until she was old enough to marry; Pirithous chose Persephone, despite her being already married to Hades. They left Helen with Theseus's mother Aethra at Aphidna, where the Dioscuri later rescued her.

The two friends then journeyed to the underworld to carry off Persephone. As they rested, Theseus sat down on a rock and felt his limbs stiffen and fix him immovably to the stone; Pirithous too was trapped. The Furies gathered around them, and Theseus was held in torment for many months. Eventually Heracles, arriving in the underworld for his twelfth labour, persuaded Persephone to forgive Theseus and freed him; but when he tried to free Pirithous the underworld shook violently, and Pirithous remained trapped forever. On returning to Athens, Theseus found that the Dioscuri had taken both Helen and his mother Aethra to Sparta.

Phaedra, Theseus's second wife and a daughter of King Minos, bore him two sons, Demophon and Acamas. While the boys were still infants, Phaedra fell in love with Hippolytus, Theseus's son by the Amazon queen Hippolyta. In some versions Hippolytus had rejected Aphrodite to become a devoted follower of Artemis, so the goddess punished him by making Phaedra love him; he rejected her advances out of chastity.

In Euripides's tragedy, Phaedra's nurse revealed her mistress's love to Hippolytus, who swore not to reveal his source. To die with dignity, Phaedra wrote a tablet to Theseus falsely claiming that Hippolytus had raped her, then hanged herself. Theseus believed the accusation and used one of three wishes Poseidon had granted him against his own son. The curse sent a sea monster, usually depicted as a bull, which frightened Hippolytus's horses and dragged him to his death. Afterwards Artemis revealed the truth to Theseus.

In the Roman playwright Seneca's version, Theseus called upon Neptune to kill his son, and on learning of Hippolytus's death Phaedra killed herself from guilt, realising she had not intended his death. In yet another version Phaedra accused Hippolytus but did not take her own life, and Dionysus sent the wild bull that terrified the horses.

A cult eventually formed around Hippolytus, connected to the worship of Aphrodite. Young women about to marry offered locks of their hair to him, and the cult believed that Asclepius had resurrected Hippolytus and that he lived in a sacred forest near Aricia in Latium.

According to some sources Theseus was one of the Argonauts, though Apollonius of Rhodes states that he was still imprisoned in the underworld at that time. With Phaedra, Theseus fathered Acamas, who later hid inside the Trojan Horse. Theseus also welcomed the wandering Oedipus and aided Adrastus in burying the warriors of the Seven Against Thebes.

Theseus was regarded in legend as the founder of Pythopolis in Anatolia. After his companion Solois died during an expedition against the Amazons, Theseus recalled a Delphic oracle instructing him to found a city whenever he suffered great sorrow in a foreign land, and so established Pythopolis, the "city of the Pythian god" (Apollo), leaving some of his followers there.

Having lost favour in Athens, Theseus was thrown from a cliff by Lycomedes on the island of Skyros, and so died. In 475 BCE, responding to an oracle, Cimon of Athens, who had conquered Skyros for the Athenians, identified what he believed to be Theseus's remains, a coffin of a great corpse with a bronze spear-head and a sword at its side, and had them reburied in Athens. In early modern times the name "Theseion" was mistakenly applied to the Temple of Hephaestus, once thought to be the site of the hero's tomb.