Jason was a person from pagan Greek mythology. He sailed on his ship the Argo (with Hercules and Orpheus and the other Argonauts) to Colchis to retrieve the Golden Fleece. King Aeetes of Colchis assigned Jason several tasks he had to perform before he could retrieve the Golden Fleece; these tasks were supposed to be impossible, but King Aeëtes’s daughter Medea had fallen in love with Jason so she aided him in the tasks. With Medea’s aid (Medea was a powerful witch), Jason won the Golden Fleece and he and Medea were married and he had two children by her. Later in his life, he divorced Medea so he could marry King Creon's daughter; in revenge for this betrayal Medea killed Jason’s new bride and both of the children she had by him, leaving him to mourn their loss. 
Jason is also a Christian name for a boy.
When Jason was a child, his father Aeson was overthrown by his brother Pelias forcing him to flee the city with Jason. When Jason had grown he went back to Iolcus to challenge his uncle Pelias for the kingship. On the way he helped an old woman across the river Anaurus and lost his other sandal. The woman revealed she was Hera and promised to give Jason her favor because Pelias did not honor her. An oracle had predicted to Pelias that he would be killed by a man who came to the city with only one sandal. He received Jason to his palace and persuaded him to go to Colchis and bring back the golden fleece of the ram that had taken his kinsman Phrixus there. Jason gathered a group of fifty heroes to go with him to Colchis, the greatest of them being Heracles, Orpheus, Castor and Polydeuces as well as Zetes and Calais, the winged sons of the north-wind Boreas and Argus, who constructed a large ship for them. It was named Argo after him, from which the heroes are called Argonauts.
Journey to Colchis
After departing from Iolcus they first arrived to the island of Lemnos. Shortly before their arrival the men of the island had arrived from a war expedition to Thracia and brought captive women with them whom they had taken as their mistresses. In jealousy, all the women of Lemnos had killed their husbands. The Argonauts were welcomed by the new Queen Hypsipyle, the daughter of the former king Thoas, as she hoped she could convince them to stay. Jason agreed and became the lover of Hypsipyle and for a time and had two sons with her, named Euneus and Nebrophonus. Heracles eventually urged the Argonauts to continue their journey and they left Lemnos.
The Argonauts next landed to an island inside the Propontis, inhabited by the Doliones, ruled by King Cyzicus. The island was also inhabited by Earthborn, giants who had six arms but the Doliones were protected from them by Poseidon from whom they were descended. The Argonauts were welcomed by Cyzicus and his wife Cleite and they stayed for the night in the king's palace. In the morning, they climbed the mountain of Didymus to see how they should continue their journey. They were attacked by the Earthborn but Heracles shot them with his bow. The Argonauts then left the island but, unbeknownst to them, the wind pushed their ship back to the island. The Doliones thought they were attacked by Pelasgians and a fierce battle followed in which Cyzicus was killed by Jason. When Cleite learned of this, she hanged herself. Before the Argonauts left the island, Hylas, the servant of Heracles had went to fetch water from a nearby spring called Pegae and naiads in the spring pulled him into the water. Heracles went in vain to search for him and the Argonauts accidentally departed without him.
The Argonauts then arrived in Bithynia where they met the soothsayer Phineus whom Zeus had made old and blind for predicting things that were forbidden for man to know. As punishment he was tormented by harpies who stole his food every day and left him barely enough to avoid starvation. Jason promised to help him and when the harpies arrived, Zetes and Calais began to chase them. The two were eventually stopped by the goddess Iris who forbade them to continue but swore that the harpies would no longer torment Phineus. In return for their help, Phineus gave them directions and warned them about the clashing rocks, two moving islands that clashed together from time to time, shattering anything between them. When they arrived near the rocks, the Argonauts released a dove which flew between the islands and only lost a few tail feathers. They then sailed through and with the help of Hera, only the prow of the Argo was shattered.
Jason and Medea
They finally arrived in Colchis and were met by its king Aeëtes and his daughter, the witch Medea. Hera decided to use her to her advantage and persuaded Eros to shoot his arrow at her, making her fall in love with Jason. Aeëtes told the Argonauts that the fleece was in a grove guarded by a dragon that never sleeps and they could only receive it by finishing the tasks he would give to them. FIrst they would have to tame two fire-breathing bulls who came there every day then use them to plow the field of Ares and sow it with the teeth of a dragon which would then grow into armed men. They would then have to defeat these men and all this was to be accomplished in one day. The following evening Medea came to meet the Argonauts and promised to help Jason if he would take her with him to Iolcus. She gave him a drug which would protect him from the bulls and advised him to throw a rock in the midst of the armed men so they would begin to fight amongst themselves and kill each other. Following Medea's advice, Jason was able to complete the tasks but Aeëtes realized Medea had helped him and refused to give the fleece. Medea and Jason decided to steal the fleece and escape during the following night. He went to the grove with Medea who gave the dragon a sleeping drug. The dragon soon fell asleep and Jason was able to take the fleece and escape with her.
Aeëtes sent his ships to chase them but Medea was able to stop them by killing her brother Apsyrtus and scattering his limbs in the sea. Enraged by the murder, Zeus sent a storm to throw the Argo off its course. The beam of the ship spoke with a human voice ordering them to visit Circe, the aunt of Medea, in order to purge themselves from the murder of Apsyrtus. The Argonauts sailed to the island of Aeaea and were met by Circe who performed the necessary sacrifices to purge them of the murder. The Argonauts continued their journey back to Iolcus. On the way they sailed past the island of Anthemoessa where the Sirens attempted to beguile them but Orpheus began to sang and drowned their voices with his song. When they stopped near Crete the bronze man Talos threatened them by throwing rocks at their ship. Medea bewitched him and as Talos moved towards Medea he grazed his ankle on a rock breaking his vein which caused his death.
When Pelias heard that Jason was returning he decided to kill Aeson. He committed suicide as did his wife but Pelias still killed their young son Promachus. Jason asked Medea to take revenge on him. She told the daughters of Pelias that she could make a drug that would make Pelias young again. She demonstrated this by slaughtering an old ram and plunging it into her kettle from which a young lamb jumped out. They went together with Medea to Pelias's bedchamber the following night and Medea killed him and threw his body into her kettle. However, she had lied to them and Pelias remained dead. Horrified by the deed, the inhabitants of Iolcus banished both Jason and Medea. They went to exile in Corinth and Jason agreed to marry Glauce, the daughter of the king of Corinth, supposedly in order to ensure the future of the two children he had with Medea. Medea was enraged at first but then pretended to accept the marriage and gave a robe as a gift to Jason's new bride. Unbeknownst to him, the robe was poisoned and Glauce died as soon as she touched it as did her father. Medea then killed her two children and escaped to Athens in her chariot drawn by dragons. Jason died soon after when his head was crushed under a beam from the Argo.
- Encyclopedia Mythica
- Apollonius Rhodius. Argonautica.
- Apollodorus. The Library.
- Ovid. Metamorphoses.
- Euripides. Medea.