We are in the King of Menfi's palace. Ramfis, head of the ministers, confesses to Radamès, a valuable chief of the pharaonic army, his fears of a new Ethiopian invasion. The king will reveal the name of the new chief of the royal army, named by Isis. Radamès dreams of being the chosen one to come back with glory and to hand back the throne and native land to the woman he loves: Aida, daughter of the king of Ethiopia, herself in love with Radamès and now captured by the Egyptians. Amneris, daughter of the king of Egypt, is in love with Radamès too and she suspects Aida, now her personal slave, to be her rival in love. Meanwhile, a messanger brings the news of new Ethiopian troops crossing the borders and marching towards Thebes. It is war. The king announces the name of the chosen hero: Radamès. Everyone celebrates apart from Aida, who is torn between the love for the father and the passion for the enemy. She asks for help to the gods but she is seen by Amneris.Inside the temple of Vulcan, between dances and prayers to God, Radamès receives from Ramfis the sword which consacrate him as leader of the Egiptian army.
Amneris is in her room, assisted by her handmaids. She is getting ready to celebrate the Egyptian victory. When Aida arrives, she shows respect for her grief and, pretending Radamès to be dead on the field, she pushes Aida to reveal her real feelings for him. Aida's candid confession is mocked and she is forced to ask for forgiveness. The crwod rushes at the gates of Thebes attracted by the ceremony of victory. The king is sitting on the throne with his daughter Amneris. There is a procession of chariots, sacred vessels, the statues of the gods and a group of dancers brings the treasures of the conquered. Radamès enters and Amneris crowns him with the crown of the winners. The king vows to fulfill his every desire. Radamés asks that the prisoners are gathered together and demand for them life and freedom, not knowing that between them lies Amonasro, the Ethiopian king, father of Aida. Ramphis is forced to please him but decides to hold hostage Aida and a warrior, actually Amonasro, who swears to have buried the king of the Ethiopians. The prisoners are freed. But another prize, unwanted and undeniable, waits for the Egyptian hero: the hand of Amneris, who is rejoicing in the victory of love, while Aida cries to her own destiny and Amonasro cries out for revenge.
A boat driven by the head of the ministers, glides over the waters of the Nile and silently lands on the sacred banks. Amneris asks the goddess to protect her upcoming marriage. But that night, on the same shores, Aida is waiting for Radamès. However, Amonasro precedes the enemy and convinces her daughter to betray her lover to save her people. It promises to be a new war, the Ethiopians are ready to attack the Egyptians. For that Aida will have to get Radamés revealing her the battle plans of the Pharaonic army. Oppressed with anguish, the slave meets her lover, she dreams with him a romantic getaway and gets the information needed by the father. Amonasro comes out of hiding where he overheared everything, introduces himself to Radamès as the king of the Ethiopians and tries to convince him to join the enemy. But Amneris, who has seen everything in secret, reports the plot to the ministers and the guards. With the help of Radamès, Aida and her father manage to escape, while he hands himself to Ramfis, resigned to pay for his guilt.
We are in the palace of the king of Egypt. Amneris orders to see the prisoner, even if she is torn between resentment and love. She wants to save him but Radamés is now determined not to oppose his own destiny, and doesn't want to hide his feelings for Aida any longer. She has survived the battle where his father has died and is about to be reunited with her people. The ministers are ready to execute the traitor; Amneris curses herself and the jealousy she has not been able to suppress and begs for mercy for the innocent Radamès. But the leader does not excuse himself and is sentenced to death. Radamès is in the crypt where he is about to be bricked in. The ministers close the crypt, Radamès calls the name of Aida for the last time and, as in a dream, the woman appears to him. It is not a vision, Aida came to die with him. The lovers embrace and greet the cruel world that has condemned them. Above them, Amneris dressed in mourning, prays at the tomb of the beloved, calling for peace.