- 1871 - Grand opéra Ramfis, the high priest of Egypt tells Radames, the young warrior, that war with the Ethiopians seems inevitable, and Radames expresses the hope that he be chosen as the Egyptian commander.
Radames dreams both of gaining victory on the battle field and of Aida, the Ethiopian slave, with whom he is secretly in love. Aida, who is also secretly in love with Radames, is the captured daughter of the Ethiopian King Amonasro, but her Egyptian captors are unaware of her true identity. Her father has invaded Egypt to deliver her from servitude. Amneris, the daughter of the Egyptian King enters the hall. She too loves Radames, but fears that his heart belongs to somebody else. Then Aida appears and, when Radames sees her, Amneris notices that he looks disturbed. She suspects that Aida could be her rival, but she is able to hide her jealousy and approaches her.
The King enters, along with the High Priest, Ramfis, and the whole palace court. A messenger announces that the Ethiopians, led by King Amonasro, are marching towards Thebes. The King declares war and also proclaims Radames to be the man chosen by the goddess Isis as leader of the army. Upon receiving the mandate from the King, Radames proceeds to the temple of Vulcan to take up the sacred arms.
Alone in the hall, Aida is torn between her love for her father, her country, and Radames.
Scene 2: Inside the Temple of Vulcan
Solemn ceremonies and dances by the priestesses take place followed by the installation of Radames to the office of commander-in-chief. All present in the temple pray for the victory of Egypt and protection for their warriors.