The sun sets over the imperial palace in a mythical Peking. A Mandarin declares that any prince wishing to marry Princess Turandot must answer her three riddles. Those who fail will lose their heads. The unsuccessful Prince of Persia will be executed at moonrise. A mass of people clamours for his blood and are violently pushed back by palace guards. In the ensuing mêlée, the slave Liù calls for help to lift her fallen master, Timur. A young Tartar prince comes to their aid and recognizes his father. Both in disguise, they were forced to flee their homeland. Only Liù has remained at Timur’s side for love of the Prince who once smiled at her. The onlookers are thrilled as the executioner’s servants sharpen the sword for the beheading, but when the Persian Prince appears, the crowd is struck by his beauty. Their cheers for his death turn to pleas that he be spared. The Unnamed Prince wishes to curse the cruel Turandot. However, when she appears to order the execution, he falls in love with her cold beauty, and he too resolves to face the Princess’s riddles. Both Timur and Liù plead that he not risk death; but his heart aches. The Emperor’s ministers Ping, Pang, and Pong also attempt to dissuade the Prince. However, their pleading is to no avail. Liù laments that the Prince’s death would break her heart, but he comforts her and asks that for his smile, she continue to care for his father. The Prince is resolved to face the test. The people of Peking rejoice in the thought of another execution, and the Prince strikes the gong, declaring his intent to court Turandot.
Late at night, in a palace pavilion, Ping, Pang, and Pong are bored with their lives at court: an endless litany of preparing either a wedding for Turandot or a suitor’s funeral. They dream of a simpler life on their country estates away from the Princess who has upset the stability of ancient China with her thirst for blood. The ministers imagine the peace should Turandot find a husband to contain her passions. But they resign themselves to another prince losing his head. The sun rises over a square within the palace wall as the imperial court convenes. The Emperor himself attempts to dissuade the Unnamed Prince. Yet he insists, and the Emperor relinquishes him to his fate as the price for his stubbornness. Turandot appears and explains the root of her cruelty. In ancient times, her ancestress Lo-u-ling was raped and killed by a foreign, Tartar prince. As vengeance, Turandot is resolved to take the life of any man who desires to possess her. She too attempts to deter her new suitor to no avail. She poses her three riddles. To her horror and to the joy of the crowd, the Prince is able to answer each one. He has won the trial, but Turandot implores her father not to give her away to the foreign prince. The Emperor insists on upholding the sanctity of his oath. Taking pity, however, the Prince offers the Princess her freedom and his head if she discovers his name by dawn. Turandot accepts the challenge to the misgivings of her father who hopes that at sunrise the Prince will be his son.
The Unnamed Prince is alone at night in the palace gardens. Turandot has sentenced the people of Peking to death should his name not be found. However, the Prince is confident that his identity is secure, and he will be victorious. Ping, Pang, and Pong attempt to bribe him to leave, while the people of Peking threaten the Prince if he does not reveal his name. Timur and Liù are brought before him. Having been seen together, it is believed that they know the Prince’s identity. Turandot asks them for his name. To protect Timur from harm, Liù confesses that she alone knows it. She is tortured but refuses to speak, claiming love gives her strength and that Turandot too will learn to love. Before the torture continues, Liù, fearful she will break, takes one of the guard’s daggers and commits suicide. In despair, Timur declares that her spirit will take revenge, and the fearful crowd attempts to placate the deceased slave, carrying her off in a funeral procession, leaving Turandot and the Prince alone. The Prince reproaches Turandot for her cruelty. Then, despite her protestations, he tears aside her veil and kisses her. Her resolve crushed, Turandot admits that the Prince’s confidence has filled her with a mixture of fear and love. She asks that he leave her vanquished. Victorious over her, however, the Prince offers up his life and reveals his name as dawn breaks: Calaf. With the Prince’s fate in her hands, Turandot rejoices. In the palace square, Turandot announces that she has discovered the Prince’s name. But rather than give him over to the executioner, she declares: «His name is Love!». The crowd celebrates the triumph of love.