Princess Turandot decreed that she will marry any prince who can solve three riddles. If the prince fails, he will be executed.

ACT I: (In front of the Imperial Palace, at moon-rise)

The scene opens on the execution of the Prince of Persia, the most recent suitor who has failed to answer Turandot's riddles. Prince Calaf is in the crowd and recognizes his long-lost father, Timur, the deposed king of Tartary, accompanied by Liù, a slave girl. Calaf is overjoyed seeing his father alive but urges him not to speak his name because he fears the Chinese rulers who have conquered Tartary. To Liù he asks why she has stood by his father for so long. She replies that it is because Prince Calaf smiled kindly on her one day.

The moon rises, and the execution proceeds. Turandot appears on the palace balcony, beautiful in the light of the moon. Prince Calaf falls instantly in love with her and as the Prince of Persia expires, Calaf vows to win Turandot for himself.

The Emperor of China's ministers try to dissuade Calaf, but he cannot be dissuaded and strikes the gong three times to signal the arrival of a new suitor.

ACT II:
Scene 1 - In front of the Imperial Palace, at moon-rise

The Imperial ministers, Ping, Pang, and Pong lament their positions in court, and the countless executions they have witnessed since Turandot first issued her decree. They long for a day when the princess, transformed by love, can return peace to China.
The palace trumpet sounds, and the ministers ready themselves for another spectacle as they await the entrance of the Emperor.

Scene 2 - The square of the Imperial Palace. Sunrise.

The Emperor Altoum, father of Turandot, sits on his grand throne in his palace. Weary of the executions, he urges Prince Calaf to withdraw his challenge. The Prince insists on proceeding.

Turandot enters and explains that, inspired by her ancestor, Princess Lou-Ling, who was cruelly betrayed by a man, she has vowed to keep herself pure. The trial begins. Turandot announces each riddle, one at a time. Prince Calaf answers each one correctly. As he completes the third and final riddle, Turandot collapses in despair and begs her father to release her from her own decree. The emperor refuses, but Prince Calaf offers release through a riddle of his own. If Turandot can discover his name by daybreak, he will forfeit and die. If not, she will be his. Turandot accepts.

ACT III:
Scene 1 - The palace gardens. Night.

Prince Calaf waits in the palace garden contemplating his victory over the princess in the famous aria "Nessun dorma." Ping, Pang, and Pong enter to tempt an answer out of the Prince. Prince Calaf is unmoved until palace guards drag in Timur and Liù, who had been seen with the Prince earlier.

Turandot also enters to question Calaf herself. Liù steps forward and announces that only she knows the Prince's name. The palace guards try to force an answer out of her, but she finds the strength to resist in her love for Calaf. Instead, she turns to Turandot telling her that through her own sacrifice, Turandot will learn to love. Liù takes a guard's dagger and stabs herself.

As Liù is carried off, everybody departs, leaving the Prince and Turandot. He kisses her in spite of her resistance. Turandot begs Calaf to leave forever. The Prince, however, reveals the answer to his riddle instead, leaving his life in Turandot's hands.

Scene 2 - The square of the Imperial Palace. Sunrise.

Turandot and Calaf approach the Emperor's throne. She proudly announces that she knows the Prince's name, but surprises everyone when she says: "His name is Love!" The crowd cheers and celebrates the two lovers.