ACT I
In ancient times, in the city of Beijing, a mandarin announces to the gathering crowd outside the Imperial Palace that any prince who wishes to marry Princess Turandot must answer three riddles. Failure to do so will result in their execution. The Prince of Persia, the most recent suitor, is to be executed at the rising of the moon. Among the spectators are a slave girl named Liù, her elderly master Timur, and a young unknown prince. The unknown prince recognizes the old man as his long-lost father. The mob calls for the death of the Prince of Persia, but as the moon rises, a fearful silence falls. The crowd pleads with the princess to spare the Prince of Persia, but Turandot appears in her palace and wordlessly orders the execution to proceed. The unknown prince becomes enchanted by Turandot's beauty and decides to win her over, to the horror of Liù and Timur. The three ministers of state, Ping, Pang, and Pong, also try to dissuade him, but he remains steadfast. He comforts Liù before striking the gong to announce his intention to compete for Turandot's hand.

ACT II
Ping, Pang and Pong cling to the hope that Turandot's heart can be melted by love, bringing peace to the kingdom, but their reverie is interrupted by the clamor of the crowd assembling for the riddle challenge. Inside the throne room, Emperor Altoum implores the unknown prince to reconsider, yet the prince persists.  Turandot enters and recounts the tale of her ancestor, Princess Lou-Ling, who was raped and killed by a conquering prince. In an act of vengeance, Turandot has vowed to never yield to a man. The riddle competition commences, and Turandot poses three enigmas. The unknown prince answers them all to Turandot's horror. The prince then presents Turandot with a challenge of his own: If she can discover his name by the break of dawn, he will pay with his life.

ACT III
A decree is issued that no one in the city may sleep until the name of the unknown Prince is revealed, and those who disobey will be executed. Calaf remains confident that he alone can reveal the truth, but Ping, Pang, and Pong try to bribe him with various rewards, including his safe escape from the city. Timur and Liù are captured because of their association with the unknown Prince, and Turandot orders Timur to be tortured until he reveals the Prince's identity. However, Liù steps forward and claims that she alone knows the Prince's name but will never reveal it. She resists progressively increasing torture, until she takes a dagger from a soldier and kills herself. The prince condemns Turandot for her cruelty and impulsively kisses her. The kiss softens Turandot, and she weeps for the first time. The Prince then reveals that his name is Calaf, putting his life in Turandot's hands. At dawn, the court assembles, and Turandot announces that she has discovered the stranger's name: Love.