Art Institute of Chicago: Leda and the Swan
Leda and the Swan is a story and a popular art subject in Greek mythology. The god Zeus, in the form of a swan, seduces or rapes Leda.
Leda bore Helen and Polydeuces, children of Zeus, while at the same time bearing Castor and Clytemnestra, children of her husband Tyndareus, the King of Sparta.
It was a well-known myth through the Middle Ages but emerged as a classic theme associated with eroticism in the Italian Renaissance.