At the ducal court of Mantua, the hunchbacked jester Rigoletto mocks the courtiers cuckolded by the profligate Duke, stirring them to plans of vengeance. Count Monterone appeals to the Duke for the return of his dishonoured daughter, but is cruelly mocked by Rigoletto. Enraged, Monterone calls down a father's curse on the terrified jester.
Outside his house, Rigoletto encounters Sparafucile, a professional assassin, but has no need of his services. Rigoletto warns his daughter Gilda to remain concealed in their home. She does not reveal to him that she has fallen in love with a handsome young man she has encountered on her way to church. The object of her affections is the Duke, who appears as soon as Rigoletto has left, bribing Gilda's nurse to admit him and to speak well of him to Gilda. He tells her he is a poor student. After he leaves, the courtiers come to abduct Gilda, believing her to be Rigoletto's mistress. They trick Rigoletto into assisting them, assuring him that it is the Countess Ceprano they are abducting from the neighbouring house. When he realizes what has happened, he is distraught. He remembers the curse.
The courtiers describe their abduction of Gilda to the Duke. He is delighted to discover that she has been brought to his palace and awaits him in his bedroom. Rigoletto now enters, feigning indifference but desperately seeking signs of the whereabouts of his daughter. When he realizes what has happened he first curses, then pleads with the courtiers for her return, but to no avail. Gilda appears en deshabillé, and Rigoletto swears vengeance on the Duke.
The Duke has been lured to a remote inn by Sparafucile's sister Maddalena. Rigoletto has paid Sparafucile to kill the Duke and to deliver his body in a sack so that he may himself throw it into the Mincio. Rigoletto brings Gilda with him to spy on the inn, hoping to reinforce the notion that the Duke is not a man of honour in affairs of the heart. Gilda is unimpressed.
Rigoletto sends her home to change into men's clothing for their flight to Verona. Infatuated with the Duke herself, Maddalena begs her brother to spare him and to murder the jester instead. His sense of professional responsibility offended, Sparafucile refuses, but does go so far as to agree that if anyone else should happen to show up at the inn on this wild and stormy night, he will murder them instead. Gilda, returning and hearing all this, sees her chance to help the man she loves. She boldly walks up to the door of the inn, knocks, is admitted and promptly stabbed and stuffed into the sack for Rigoletto. Rigoletto is just about to throw the sack in the river when he hears the Duke still singing in the inn. Wildly he opens the sack to find his dying daughter, who with her last breath assures him that she will pray for him with her mother in heaven. Again, Rigoletto recalls Monterone's curse.