- 1842 
- English translation - German translation - Spanish translation - Verdi described this opera as the genuine beginning of his artistic career.
- Each act of the libretto of this opera by Verdi is prefaced by an appropriate quotation from the Book of Jeremiah, but curiously, the biblical chapter citations are wrong in three of the four cases.
The Jews are being defeated and Nabucco (Nebuchadnezzar) is poised to enter Jerusalem. The High Priest Zaccaria tells the people not to despair but to trust in God: D'Egitto là su i lidi / "On the shores of Egypt He saved the life of Moses". The presence of a hostage, Fenena, younger daughter of Nabucco, may yet secure peace (Aria: Come notte a sol fulgente / "Like darkness before the sun, like dust before the wind"). Zaccaria entrusts Fenena's safety to Ismaele, nephew of the King of Jerusalem and a former envoy to Babylon. Although Fenena and Ismaele love each other, when they are left alone, Ismaele urges her to escape rather than risk her life. Nabucco's elder daughter, Abigaille, storms into the temple with soldiers in disguise. She, too, loves Ismaele. Discovering the lovers, she threatens Ismaele: if he does not give up Fenena, Abigaille will accuse her of treason. The King himself enters (Viva Nabucco / "Long live Nabucco"). Zaccaria defies him, threatening to kill Fenena with a dagger. Ismaele intervenes to save her. Nabucco responds by ordering the destruction of the temple, and the Jews curse Ismaele as a traitor.
Act 2
Scene 1: The Palace in Babylon
Nabucco is away at the wars and has appointed Fenena as regent. Abigaille has discovered a document that proves she is not Nabucco's real daughter, but a slave (Aria: Anch'io dischiuso un giorno / "I too once opened my heart to happiness"). The High Priest of Baal, accompanied by the Magi, comes to tell Abigaille that Fenena has released the Jewish captives. Their response is to launch a coup to put Abigaille on the throne, while spreading a rumour that Nabucco has died in battle, and they leave Abigaille to sing the cabaletta: Salgo già del trono aurato / "I am ready to ascend the bloodstained seat of the golden throne").
Scene 2: A hall in the Palace in Babylon
Accompanied by a cello sextet, Zacharia awaits Fenena (Vieni, o Levita / "Bring the tables of the law"). She converts to the Jewish religion, and Ismaele is reconciled to the Jews. However, it is announced that the King is dead and Abigaille and the High Priest of Baal demand the crown from Fenena. Unexpectedly, Nabucco himself enters, scorning both sides, both Baal and the Hebrew god that he has defeated. He declares himself God. When Zaccaria objects, Nabucco orders the Jews to be put to death. Fenena says that she will share their fate. Repeating that he is now god: Non son piu re, son dio / "I am no King! I am God!"), Nabucco is promptly hit by a thunderbolt and loses his senses. The crown falls and is picked up by Abigaille.
Act 3
Scene 1: The Hanging Gardens of Babylon
The High Priest of Baal presents Abigaille with the death decree for the Jews and Fenena. Nabucco enters looking like a mad man, claiming his throne. Abigaille persuades him to seal the decree, but he asks that Fenena be saved. He tells Abigaille that she is not his true daughter but a slave. Abigaille mocks him, destroying the document with the evidence of her true origins. Understanding that he is now a prisoner, he pleads for Fenena's life. (Duet: Oh di qual onta aggravasi questo mio crin canuto / "Oh what affront I must suffer in my old age"). Abigaille exults.
Scene 2: Banks of the River Euphrates
The Jews long for their homeland: Va pensiero, sull'ali dorate / "Fly thought on golden wings; Fly and settle on the slopes and hills"). Zaccaria once again exhorts them to have faith: God will destroy Babylon.
Act 4
Scene 1: The Palace in Babylon
Nabucco awakens, his strength and his reason fully regained. He sees Fenena in chains being taken to her death. Asking forgiveness of the God of the Jews, he promises to rebuild the temple in Jerusalem, and follow the true faith (Dio di Giuda / "God of Judah! The altar, your sacred Temple, shall rise again"). Joined by loyal soldiers, he resolves to punish the traitors and rescue Fenena.
Scene 2: The Hanging Gardens of Babylon
As Zaccaria leads Fenena and the Jews towards death (Va! La palma del martirio......dischius'è il firmamento / "Go, maid, go and conquer the palm of martyrdom"...."Oh, heaven has opened up! My soul yearns for the Lord") on the sacrificial altar of Baal, Nabucco rushes in, sword in hand. At his word the Idol of Baal shatters into pieces. Nabucco tells the Jews they are free and a new Temple will be raised to their God. Abigaille enters. She has poisoned herself. She expresses her remorse, asks the forgiveness of Fenena and dies. Zaccaria acclaims Nabucco as the servant of God and the King of Kings.
| Nabucco | Baritone | M-L | King of Babylon |
| Abigaille | Soprano | F-H | Supposedly the elder daughter of Nabucco |
| Fenena | Mezzosoprano | F-M | Daughter of Nabucco |
| Ismaele | Tenor | M-M | Nephew of the King of Jerusalem |
| Zaccaria | Bass | M-VL | High priest of the Jews |
| Anna | Soprano | F-H | Zaccaria's sister |
| Abdallo | Tenor | M-M | Babylonian soldier |
| High priest of Baal | Bass | M-VL |
| Va, pensiero (Chorus of the Hebrew slaves) |