Zephyrus, sometimes known in English as just Zephyr (Ζέφυρος, Zéphyros), 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.

In the story of Cupid and Psyche, Zephyrus served Eros (or Cupid) by transporting Psyche to his abode.

Zephyrus' Roman equivalent was Favonius (the 'favouring') who held dominion over plants and flowers. The Roman poet Horace writes: