Zephyrus, sometimes known in English as just Zephyr, in Latin Favonius, is the Greek god of the west wind. The gentlest of the winds, Zephyrus is known as the fructifying wind, the messenger of spring. It was thought that Zephyrus lived in a cave in Thrace.

Zephyrus was reported as having several wives in different stories. He was said to be the husband of Iris, goddess of the rainbow. He abducted the goddess Chloris, and gave her the domain of flowers. With Chloris, he fathered Karpos ("Fruit"). He is said to have vied for Chloris's love with his brother Boreas, eventually winning her devotion. Additionally, with yet another sister and lover, the harpy Podarge (also known as Celaeno), Zephyrus was said to be the father of Balius and Xanthus, Achilles' horses.

One of the surviving myths in which Zephyrus features most prominently is that of Hyacinth. Hyacinth was a very handsome and athletic Spartan prince. Zephyrus fell in love with him and courted him, and so did Apollo. The two competed for the young man's love, but he chose Apollo, driving Zephyrus mad with jealousy. Later, catching Apollo and Hyacinth throwing a discus, Zephyrus blew a gust of wind at them, striking Hyacinth in the head with the falling discus. When Hyacinth died, Apollo created the hyacinth flower from his blood. Apollo was furious, but Eros protected Zephyrus, as the act was committed in the name of love, on the condition that the wind god served Eros forever.