Galatea (soprano), Acis (tenor), Damon (tenor), Polyphemus (bass), Coridon (tenor)
A group of youths and nymphs is celebrating their carefree life and the joy of nature. Among them is Galatea, who is unable to join in their happiness as she is separated from her love Acis. The birds are chirping their cheerful song, awakening her desire for him. She attempts to persuade the birds to cease their chorus.
As Acis seeks for Galatea, his friend Damon tries to persuade him to abandon his search and join his fellows in their celebrations instead. But Acis now sees his Galatea and praises her beauty. The lovers are reunited, and they declare their love for each other.
But their happiness is short-lived when the giant Polyphemus comes stalking through the forest with the intent of having Galatea for himself. When he is rejected, the youth Coridon advises him to be gentler in his wooing. But Acis leaps to Galatea’s defence. Damon once again reminds him that love is fleeting, but Galatea interrupts him, declaring her constancy to Acis.
As Acis and Galatea declare their fidelity to each other, they are interrupted by the jealous Polyphemus who hurls a rock at Acis and kills him. The young people mourn his death. Galatea joins in lamentation. They try to comfort her and remind her that she can save Acis with her divine powers. Galatea summons her powers and transforms the lifeless Acis into a beautiful fountain.