Ancient Egypt. The young warrior Radamès dreams of leading the army to victory to win the heart of his secret love: Aida, a slave to Amneris (daughter of the Pharaoh), who herself is in love with (and jealous of) Radamès. When news arrives of Ethiopia's invasion of Egypt, the King appoints Radamès as supreme commander and calls for war. Aida (who is actually an Ethiopian princess) is torn between her love for Radamès and her loyalty to her homeland.
Scene II: At the Temple of Vulcan, a solemn ceremony unfolds, wherein Radamès is bestowed with the investiture and the revered sacred sword.
Scene I:
Amidst joyful song and dance, Amneris eagerly awaits the victorious army's return. Aida arrives, and with suspicions of her being a romantic rival, the princess cunningly tricks her into confessing her feelings for Radamès. This ignites a wrathful fury in Amneris, yet the arrival of the troops interrupts their confrontation.
Scene II:
Radamès's victory is celebrated with grandeur, and the Pharaoh offers him any reward he wishes. Among the captives from Ethiopia is King Amonasro, Aida's father, whose true identity remains concealed from the Egyptians. Radamès requests freedom for all prisoners, a wish granted by the Pharaoh. In return, he is promised Amneris's hand in marriage. However, the High Priest Ramfis intervenes, ensuring that Aida and her father remain captive.
While Amneris prays at the Temple of Isis, Aida ventures to the banks of the Nile, where Radamès has arranged to meet her. She first reminisces about her distant homeland and is then joined by her father, who, through a mix of flattery and threats, persuades her to find out the location of the Egyptian army from Radamès. When Radamès arrives, Aida convinces him to flee with her using a safe route without any fear of discovery. Unaware of the deception, he reveals it to her. Amonasro rejoices, and Amneris, emerging from the temple, discovers everything. Aida and her father escape, while Radamès surrenders himself to the guards.
Scene I:
Torn between love and anger, Amneris begs Radamès to deny the charges of treason, disclosing that Amonasro is dead but Aida is still alive. He rejects her plea and confronts the judgment of the priests, led by Ramfis. The verdict is dire: he is to be buried alive. Amneris's despair proves futile, and the sentence is final.
Scene II:
Buried beneath the Temple of Vulcan, Radamès learns that Aida has hidden herself in the tomb to join him in death. Together, the two lovers bid farewell to life, yearning for happiness in the afterlife while Amneris beseeches Isis to grant eternal peace to her beloved.