The son of Athamas and Nephele.
Athamas divorced Nephele and married Ino, who wished to kill Phrixus. She convinced all of the women in the land to parch the grain set aside for the next year's crops. In the following year, when the grain would not grow, Athamas sent envoys to the Oracle at Delphi to ask what was wrong. Ino bribed the envoys to tell the king on their return that his son Phrixus must be sacrificed.
Athamas was then forced by his starving people to order the sacrifice of his son. Nephele, wishing to save her son, took Phrixus and his sister Helle and sent them away on a golden ram, a gift to her from Hermes.
While the ram was crossing the strait between Greece and Asia, Helle lost her grip and fell to her death. It is from this that the Hellespont (the sea of Helle) getis it's name. Phrixus, on the other hand, arrived safely at Colchis and was greeted warmly by king Aeetes, who gave to Phrixus his daughter Chalciope. To repay Aeetes for his kindness, Phrixus sacrificed sacrificed the golden ram, and gave its golden fleece to the king. Aeetes nailed the fleece to an oak in a grove sacred to Ares.
With Chalciope, Phrixus had four sons, who later joined with the Argonauts on their quest to gain the golden fleece.
Apollonius Rhodius. Argonautica.