The story of Medea begins with the arrival of the Argonauts in Colchis, led by Jason. King Aeetes, Medea's father and Circe's brother, agrees to give her the Golden Fleece on condition that Jason accomplish three tasks: tame two enormous bulls, spitting fire from their nostrils; force the two beasts to plow a field with a plow; and finally, sow a bag of dragons' teeth in the furrows which will then germinate and give birth to an army of warriors. King Aeetes thinks he is sending Jason to certain death by setting him these insurmountable tests.

But Medea, his daughter, has fallen madly in love with Jason. She finds him in secret and offers to use her magic powers to help him and sets as a condition that he take her with him and marry her. Seduced, the hero accepts and succeeds in the king's mission.

Jason now demands his due from Aeetes. But furious, he refuses to give Jason the Golden Fleece and threatens him with death. Jason, Medea and the Argonauts seize the Golden Fleece and flee. Medea has taken Absyrtos, her younger brother, as a hostage. Aeetes sets off in pursuit of them. Medea then helps the Argonauts escape by killing and dismembering Absyrtos, her own brother. Possessed by a murderous passion, she cuts him into pieces which she leaves behind her, thus delaying the pursuers who stop each time to recover the pieces of his remains and offer the heir to the throne a decent burial. Jason, Medea and the Argonauts thus lose their pursuers.

Back in Iolcos, Jason finds that Pelias has taken advantage of his absence to kill his father and get rid of his family. He asks Medea again to help him get revenge. She then goes to find Pelias' four daughters and pretends to be an envoy of Artemis, charged with giving their old father a new lease on life. In front of the young girls, the sorceress prepares a cauldron of boiling water, throws magic herbs into it, and has an old ram brought to her, which she slaughters and cuts into pieces, then throws into the pot. A few moments later, a very young lamb emerges from the boiling water. Medea then gives Pelias' amazed daughters the magic herbs, telling them to do the same with their father. They go to their father's apartments, blinded by their desire to make their father young again, they surround him, immobilize him, and then slaughter him. They then dismember his body before throwing the pieces into boiling water mixed with magic herbs. Pelias of course never comes out of this broth and his daughters are cursed by the Erinyes, goddesses of vengeance, for this parricide.

Medea is denounced by Pelias' daughters, and she and Jason are banished from the city. They then take refuge in Corinth, where they are welcomed by King Creon. Jason and Medea live peacefully for a few years, protected by the king. They have two boys together: Mermeros and Pheres.

Alas, one day Jason falls in love with Creon's daughter, Creusa. The king, having no heir, willingly accepts this union, rejoicing that the handsome and strong Jason becomes his successor. Jason then repudiates Medea and marries Creusa as a second wife.

Medea is destroyed: the man for whose love she killed her brother, betrayed her father, her country, her people, the one she has always followed with passion, has finally gotten rid of her. Furthermore, rejected since forever by the Corinthians because she was a foreigner, she is unceremoniously chased out of the city with her two children. Mad with rage and grief, Medea takes revenge by killing her rival: she offers Creusa a magic tunic which, barely put on, bursts into flames, burning its wearer as well as her father, then sets fire to the royal palace.

Threatened with death by the Corinthians, Medea finds refuge with Aegeus, king of Athens. The latter ardently desires a son and agrees to marry her after Medea promises to give him an heir. A child, Medos, will indeed be born shortly after, for whom Medea hopes a royal destiny.

However, the arrival of Theseus, son of Aegeus, in Athens upsets her plans. After several unsuccessful attempts to remove him, Medea then seizes the treasury of Athens, stealing a large quantity of diamonds. In her flight on her fiery chariot pulled by cobras, she lets half of this royal treasure escape.

Medea and her son Medos then head for Colchis, whose throne is then occupied by Perses, who had dethroned his father Aeetes after the flight of the Argonauts. She kills him and restores power to her father Aeetes. The end of Medea's life is little known, because Euripides' version does not specify anything about her death or the end of her life.