Which hero embarked on a quest for the golden fleece?

The hero who embarked on a quest for the Golden Fleece is Jason. In Greek mythology, Jason is best known for leading a group of heroes called the Argonauts on an adventurous journey to retrieve the Golden Fleece from the distant land of Colchis. This quest is central to the myth of Jason and the Argonauts, highlighting themes of bravery, teamwork, and the pursuit of glory.

Jason's journey is marked by numerous challenges and encounters with mythical beings, showcasing his leadership and determination. The Golden Fleece itself symbolizes authority and kingship, and retrieving it was a way for Jason to reclaim his rightful place on the throne of Iolcus.

Hercules, Theseus, and Odysseus are also significant figures in mythology but are known for different quests and adventures. Hercules is famous for his Twelve Labors, Theseus for his adventures including the Minotaur, and Odysseus for his epic journey home in the "Odyssey." Thus, Jason is the correct answer regarding the quest for the Golden Fleece.