In the myth of Theseus, which monster did he fight in the labyrinth?

The fight between Theseus and the Minotaur is one of the most famous stories in Greek mythology. Theseus uses a thread of string supplied by Princess Ariadne in order to find his way in and out of the Labyrinth. In the center of the giant maze, he heroically overcomes the great and mighty beast, freeing the children of Athens once and for all. The valiant hero leaves with the princess, while the death of the monster signals the beginning of the end for Crete. Asterion, the Minotaur of Crete, was a half-man, half-bull creature born as punishment. King Minos of Crete had offended the sea god Poseidon by refusing to sacrifice the great Cretan Bull. As punishment, Poseidon cursed Queen Pasiphae to fall in love with the bull.

Source: History Cooperative