In Greek mythology, Zeus's protective shield or breastplate was called the aegis.
The aegis was a divine protective object associated primarily with Zeus and, in later traditions, with Athena. Ancient descriptions connect it with the skin of the she-goat Amalthea, who nourished the infant Zeus. It could also bear the terrifying Gorgon head, whose image added magical protection.
Because Athena often carries or wears the aegis in art, many readers assume it belonged exclusively to her. In earlier mythological traditions, however, Zeus is one of its principal owners. The object could appear as a shield, cloak, or protective covering rather than having one fixed physical form.
The word survives in modern English in the phrase “under the aegis of,” meaning under the protection or sponsorship of someone powerful. It is distinct from Hermes's caduceus and from the Golden Fleece sought by Jason.