The significance of the Golden Fleece in ancient Greek mythology lies in its association with kingly power and purification. It is the quest of Jason and the Argonauts, representing the ultimate challenge for heroes. The Fleece is a symbol of divine favor and the right to rule, being guarded by a dragon in the land of Colchis. Retrieving it signifies not only the hero's strength but also their ability to overcome daunting obstacles, underscoring themes of adventure and sacrifice.