Act I
Ginevra tells Dalinda that she is in love with Ariodante and that they have the blessing of her father, the King. Polinesso expresses his love for Ginevra, who rejects him and it is Dalinda who then tells Polinesso that Ariodante is his rival, at the same time hinting at her own feelings for Polinesso. He decides to use Dalinda to destroy Ariodante. Ariodante and Ginevra are overjoyed when the King announces that their wedding will be celebrated the next day. Polinesso leads Dalinda to believe he loves her. Lurcanio, Ariodante’s brother, confesses to Dalinda that he loves her, but she rejects him. Ariodante and Ginevra celebrate their wedding eve.
Act II
Later that night, Polinesso tells Ariodante that he is already Ginevra’s lover and does not understand how Ariodante is marrying her. Ariodante conceals himself and Dalinda, disguised as Ginevra, invites Polinesso into her room. Ariodante feels that he has been betrayed and is grief-stricken. Lurcanio, who has watched all of this, prevents Ariodante from killing himself, convincing him instead to seek revenge. News is brought to the King that Ariodante has jumped from a cliff into the sea and is presumed drowned. Ginevra collapses in grief while Lurcanio claims that Ariodante has killed himself because of Ginevra’s infidelity.
Act III
Ariodante has survived but is in torment. He meets Dalinda, who now understands Polinesso's trickery and reveals it all to Ariodante. Polinesso challenges Lurcanio’s story. They will duel, with Polinesso as Ginevra’s champion. In spite of her resistance, the King insists. During the duel, Lurcanio fatally injures Polinesso. A new challenger appears who reveals himself to be Ariodante and promises to explain everything, as long as Dalinda is forgiven her innocent part in Polinesso’s deception. Polinesso dies, having confessed everything. The King forgives Dalinda and proclaims the triumph of love and innocence.