Which Harry Potter book introduces the Triwizard Tournament?

Harry Potter and the Goblet of Fire introduces the Triwizard Tournament.

The fourth Harry Potter novel, published in 2000, centers on an international magical competition hosted at Hogwarts. Traditionally, one champion is selected from each of three participating schools: Hogwarts, Beauxbatons Academy of Magic, and Durmstrang Institute.

Harry is unexpectedly chosen as a fourth champion, despite being under the usual age requirement and not entering his name himself. The tournament’s three tasks test different forms of magical skill and culminate in a dangerous encounter connected to Lord Voldemort’s return.

The Goblet of Fire is also the first novel to show the Quidditch World Cup in detail and to introduce Rita Skeeter as a prominent reporter. The tournament should not be confused with an ordinary Hogwarts house competition; it is an interschool event.