In Harry Potter and the Goblet of Fire, what tournament does Harry unexpectedly enter?

Harry unexpectedly enters the Triwizard Tournament in Harry Potter and the Goblet of Fire.

The tournament is an international magical competition involving champions from three schools: Hogwarts, Beauxbatons, and Durmstrang. The selected champions must complete three dangerous tasks during the school year. The Goblet of Fire chooses Viktor Krum for Durmstrang, Fleur Delacour for Beauxbatons, and Cedric Diggory for Hogwarts before selecting Harry as a second Hogwarts champion.

Harry is underage and did not submit his name, but the magical contract connected with selection forces him to compete. The tasks involve a dragon, a lake rescue, and a maze. The final task is secretly manipulated so that Harry and Cedric reach a Portkey leading to a graveyard, where Voldemort regains a body. The Quidditch World Cup is a separate event held earlier in the same novel.