Act 1:
Ginevra, daughter of the King of Scotland, tells her lady-in-waiting Dalinda that she and Prince Ariodante are in love. When Polinesso, the Duke of Albany, enters Ginevra’s bedroom unannounced and declares his love for her, Ginevra firmly rejects him. Dalinda tells Polinesso that since Ginevra loves Ariodante, the Duke should instead turn his attentions to her lady-in-waiting. Alone, Polinesso forms a plan to use Dalinda’s love for him to destroy Ariodante, marry Ginevra and gain the throne. Ariodante and Ginevra are overjoyed when the King tells them not only that their wedding can take place the following day, but also that Ariodante is to inherit the throne. Polinesso lets Dalinda believe that he loves her, but only after she promises to appear later that night dressed in Ginevra’s clothes. Lurcanio, Ariodante’s brother, tells Dalinda that he is in love with her, but she tells him to look elsewhere. In the presence of the King and the entire court, Ariodante and Ginevra celebrate their future wedding.

Act 2:
Later that night, Polinesso questions Ariodante about his impending marriage, insinuating that he is already Ginevra’s lover. Ariodante challenges him to fight, but Polinesso tells the distraught prince to hide instead and observe Ginevra’s behavior. Ariodante is then horrified to see his fiancée, who is really Dalinda in disguise, invite Polinesso into her bedroom. Lurcanio has also been tricked by Polinesso’s mise‑en‑scène, and prevents his grief-stricken brother from killing himself. Polinesso gloats over the success of his plan. The next morning, the King’s private secretary Odoardo brings the news that Ariodante has drowned himself. When the King breaks the news to Ginevra, she collapses in grief and is carried from the room. Lurcanio demands justice from the King. Claiming that Ginevra’s infidelity was the sole cause of his brother’s suicide, he declares that he will fight anyone who dares to defend her. When Ginevra appears, the King accuses her of immorality and refuses to speak to her. The grief-stricken Ginevra, shocked by the death of Ariodante and her father’s inexplicable rejection, loses her mind.

Act 3:
Ariodante has survived his suicide attempt and is lost in the forest. He saves Dalinda from assassins, hired by Polinesso to silence her. When Dalinda confesses that she disguised herself as Ginevra, Ariodante understands how Polinesso has manipulated them all. The King refuses to speak to his daughter until a champion can be found. Polinesso offers to defend Ginevra’s honour and fight Lurcanio. Brought before her father, Ginevra refuses to accept Polinesso as her champion, but the King insists on it. Lurcanio fights Polinesso, who is fatally wounded. Ginevra’s cause seems lost when suddenly an unknown man enters to challenge Lurcanio: it is Ariodante. Odoardo prevents the two brothers from fighting, bringing news that Polinesso confessed to his crimes before dying. As the King leaves to find Ginevra, Ariodante rejoices. Dalinda, alone with Lurcanio, gladly accepts his love, and repents her past behaviour. Reunited with Ginevra, Ariodante begs forgiveness for having doubted her. The two brothers and their wives‑to-be celebrate their future together, leaving the court to rejoice in the happy ending.