After describing his latest attraction to a girl he saw at church, the Duke proceeds to seduce the Countess Ceprano while her husband is cruelly mocked by the court jester, Rigoletto. One of the other courtiers announces to everyone’s amazement that the hunchback jester has hidden away a mistress. Led by cuckolded Ceprano, the courtiers vow revenge on the hated Rigoletto only to be interrupted by Monterone, who violently berates the Duke for dishonoring his daughter. Mimicked and insulted by Rigoletto, Monterone curses both men. The Duke shrugs it off while Rigoletto is deeply disturbed. Later that evening, haunted by Monterone’s curse, Rigoletto is approached by the professional assassin Sparafucile, who offers his services. After rejecting Sparafucile’s proposition (for the moment), Rigoletto is greeted by his daughter, Gilda, whom he obsessively protects and shelters from the corruption of the outside world. But the Duke (disguised as a student) has bribed Gilda’s duenna and makes contact with the girl he saw in church. Their ecstatic meeting is cut short by the approaching courtiers, who have come to carry off the woman they still think is Rigoletto’s mistress. Rigoletto unexpectedly returns and is duped into believing he is aiding in the planned capture of the Countess Ceprano. Gilda is abducted and Rigoletto, finally realizing the true situation, finds the house deserted and his daughter gone.
The courtiers bring Gilda back to the ducal palace. When Rigoletto, crazed with grief and apprehension, seeks his daughter, he finds that she is with the Duke. She admits to her father that, in spite of everything, she is still in love with her seducer. Rigoletto vows a terrible revenge for the dishonor.
Having now enlisted the services of Sparafucile, Rigoletto attempts to convince Gilda of her lover’s betrayal by showing her the Duke’s involvement with Maddalena (Sparafucile’s sister). Rigoletto sends Gilda away so she will not see the murder. But she returns and, overhearing the plotting of Sparafucile and Maddalena, resolves that she must prevent her lover’s death.