A crowd waits outside the Imperial Palace, eager for the execution of the latest suitor for the hand of Princess Turandot. She has agreed to marry the first man of royal blood who can solve her three riddles, with the losers to be put to death, and none has so far succeeded. The aged Timur, deposed King of Tartary, and his servant girl Liu are in the crowd. They spot Calaf, Timur’s long-lost son. Despite Liu’s love for him, Calaf has become obsessed with Turandot and strikes a large gong three times, giving the signal that he will try to solve the deadly challenge.

Emperor Altoum attempts to persuade Calaf to abandon his quest, but without success. Turandot puts the three riddles to Calaf, who astonishes her by solving each of them. The desperate Princess pleads to be released from her pledge of marriage and Calaf offers her a solution – he will let himself be executed if Turandot can discover his name before dawn breaks.

The city’s population searches frantically for Calaf’s name, under Turandot’s threat of death if it is not discovered, while Calaf anticipates victory. Guards bring in Timur and Liu, and Turandot threatens to torture Timur if he does not reveal the name. Liu claims that she alone knows the answer. Afraid that she might cause Calaf’s death if she confesses, Liu grabs a soldier’s dagger and stabs herself. As her body is taken away, the population departs, leaving Calaf alone with Turandot. Despite her protests, Calaf kisses her passionately and she begins to respond. As dawn breaks, Calaf reveals his name to her. Altoum and his retinue return and Turandot announces that she has discovered the answer – the prince’s name is “Love.”