A room in the palace. The Duke has seen an unknown beauty in the church and desires to possess her. He also pays court to the Countess Ceprano. Rigoletto, the hunchbacked jester of the Duke, mocks the husbands of the ladies to whom the Duke is paying attention, and advises the Duke to get rid of them by prison or death. The noblemen resolve to take vengeance on Rigoletto, especially Count Monterone, whose daughter the Duke had dishonoured. Monterone curses the Duke and Rigoletto.
A street; half of the stage, divided by a wall, is occupied by the courtyard of Rigoletto’s house. Thinking of the curse, the jester approaches and is accosted by the bandit Sparafucile, who offers his services. Rigoletto contemplates about the similarities between the two of them - Sparafucile uses his sword, Rigoletto his tongue and wits to fight. The hunchback opens a door in the wall and visits his daughter Gilda, whom he is concealing from the prince and the rest of the city. She does not know her father’s occupation and, as he has forbidden her to appear in public, she has been nowhere except to church. When Rigoletto has gone the Duke enters, hearing Gilda confess to her nurse Giovanna that she feels guilty for not having told her father about a student she had met at the church, but that she would love him more if he were poor. Just as she declares her love, the Duke enters, overjoyed, convincing Gilda of his love, though she resists at first. When she asks for his name, he hesitantly calls himself Gualtier Malde. Steps are overheard and, fearing that her father has returned, Gilda sends the Duke away after they quickly repeat their love vows to each other. Later, the hostile noblemen seeing her at the wall, believe her to be the mistress of the jester. They abduct her, and when Rigoletto arrives they inform him they have abducted the Countess Ceprano, and with this idea he assists them in their arrangements. Too late Rigoletto realises that he has been duped and, collapsing, remembers the curse.
The Duke hears that Gilda has been abducted. The noblemen inform him that they have captured Rigoletto’s mistress and by their description he recognises Gilda. She is in the palace, and he hastens to see her, declaring that at last, she will know the truth and that he would give up his wealth and position for her who had first inspired him to really love. The noblemen, at first perplexed by the Duke?s strange excitement, now make sport of Rigoletto. He tries to find Gilda by singing, and as he fears she may fall into the hands of the Duke, at last acknowledges that she is his daughter, to general astonishment. Gilda arrives and begs her father to send the people away, and acknowledges to him the shame she feels of finding out his profession. The act ends with Rigoletto’s oath of vengeance against his master.
A street. The half of the stage shows the house of Sparafucile, with two rooms, one above the other, open to the view of the audience. Rigoletto enters with Gilda, who still loves the prince. Rigoletto shows her the Duke in the house of the bandit amusing himself with Sparafucile’s sister Maddalena, half-drunk in despair over losing Gilda. The Duke then sings the most famous aria of the opera, La donna e mobile, explaining the indifelty and fickle nature of women. Rigoletto bargains with the bandit, who is ready to murder his guest, whom he does not know, for money. Rigoletto orders his daughter to put on man’s attire and go to Verona, whither he will follow later. Gilda goes, but fears an attack upon the Duke, whom she still loves, despite believing him to be unfaithful. Rigoletto offers the bandit 20 scudi for the death of the Duke. As a thunderstorm is approaching, the Duke determines to remain in the house, and Sparafucile assigns to him the ground floor as sleeping quarters. Gilda returns disguised as a man and hears the bandit promise Maddalena, who begs for the life of the Duke, that if by midnight another can be found to take the Duke’s place he will spare his life. Gilda resolves to sacrifice herself for the Duke and enters the house. When Rigoletto arrives with the money he receives from the bandit a corpse wrapped in a bag and rejoices in his triumph. He is about to cast the sack into the river, weighting it with stones, when he hears the voice of the Duke singing a reprise of his bitter aria as he leaves the house. Bewildered, he opens the bag and to his despair discovers the corpse of his daughter, who for a moment revives and declares she is glad to die for her beloved. As she breathes her last, Rigoletto exclaims in horror, "The curse!" which is fulfilled upon both master and servant.