A petasos or petasus (Greek: πέτασος) is a sun hat of Thessalian origin worn by the ancient Greeks, often in combination with the chlamys cape. It was usually made of wool felt, leather or straw, with a broad, floppy brim. It was worn primarily by farmers and travellers, and was considered characteristic of rural people. As a winged hat, it became the symbol of Hermes, the Greek mythological messenger god (Roman equivalent Mercury).
A type of metal helmet worn by Athenian cavalry was made in the shape of a petasos. Some examples have holes around the outer edge of the brim, presumably so a fabric cover could be attached. These are known from reliefs and vase paintings, with at least one archaeological example found in an Athenian tomb.
Hermes wearing petasos with caduceus
Views of a petasos
Petasos-wearing youth with spear and leopardskin
Cavalryman with petasos dangling over the back