Act One
High Priest Ramfis, a close adviser of the Egyptian royal family, tells the young officer Radamès that a new war against the Ethiopians is imminent and that the commander’s name will soon be announced. Radamès hopes to be able to lead the Egyptians into war as their general. He dreams of victory and glory, as well as his secret love for the Ethiopian princess Aida, who is living at court as a slave. Following victory over the Ethiopians, he intends to place a crown on her head and build a throne close to the sun. Amneris, daughter of the king of Egypt, is in love with Radamès and entertains hopes of winning his affections. When she encounters him in a euphoric state and he is joined by Aida, she senses the love between Aida and Radamès – which both attempt to conceal. After a messenger reports that Ethiopian troops have invaded the country, the king adjures his people to go to war with Ethiopia. Radamès is proclaimed commander. War fever breaks out, culminating in the general battle cry of “Ritorna Vincitor” (Return victorious!), which Aida also enthusiastically joins. Aida is aghast that she hopes the man going to war against her own people will be victorious. Distressed by having to choose between her lover and her fatherland, she longs for death. The priestesses and priests call on their god for assistance. In a solemn ceremony, Radamès is prepared for war and equipped with sacred weapons.

Act Two
The women are waiting for the victorious troops to return from the war. Amneris dreams of a future with Radamès, but she is jealous of Aida and attempts to find out whether she too is in love with Radamès. Amneris lies to Aida, telling her that Radamès is dead. Aida is horrified and thus betrays her feelings for Radamès. Confident of victory, Amneris reveals herself as Aida’s rival. Radamès returns from the war. He hears the Egyptian people rejoicing. As thanks for his victory, the king promises to fulfil the commander’s every wish. Radamès asks for the release of the Ethiopian captives, one of whom is Amonasro, king of Egypt and Aida’s father, who is disguised as a common soldier. While the priests demand that the Ethiopians be put to death, the populace begs for mercy for the prisoners. Ramfis suggests a compromise: only Aida and her father shall remain in the hands of the Egyptians. In reward for his victory, the king gives Radamès his daughter Amneris in marriage. Amneris is triumphant.

Act Three
On the eve of the wedding, Amneris and Ramfis implore the gods to look favourably upon them. Bereft of any hope for the future, Aida is waiting for Radamès. She reminisces about the beauties of her homeland. Rather than her lover, Amonasro is the first to appear. He appeals to his daughter not to abandon her fatherland and demands that she coax the Egyptians’ secret war plans out of her lover. Radamès encounters Aida. He confesses his love for her, which she reciprocates, but believes to be utterly hopeless. She persuades him to escape with her and at the last minute asks which route the Egyptian army is travelling. Radamès discloses the state secret. Amonasro, who has overheard him, comes forward. He is joined by Amneris and Ramfis. Radamès recognises that he has betrayed a secret and surrenders himself to the High Priest.

Act Four
Radamès is charged with treason. Amneris tries desperately to dissuade him from his confession and to win his affections. He refuses. The priests sit in judgement on Radamès and pronounce their verdict: the traitor is to be buried alive. Amneris curses the priests and their judgements. Having been walled in, Radamès awaits death. Suddenly he discovers Aida. She has come to die with him. Aida and Radamès bid the earth “Farewell.” They see the heavens opening up to them and their souls flying into the light of eternity. Amneris appeals for peace for the pair.