Theseus’s father in Greek mythology was Aegeus, the king of Athens. Aegeus is closely connected with the Minotaur story because Athens was required to send young people to Crete as tribute to King Minos.
Theseus later volunteered to join the tribute mission, intending to kill the Minotaur and end Athens’s obligation. Before the voyage, Aegeus asked him to display white sails if he returned alive. Theseus defeated the Minotaur but forgot to change the sails, leading Aegeus to believe his son had died.
Aegeus then threw himself into the sea, which Greek tradition says was thereafter called the Aegean Sea. Some versions give different details about the tribute and the voyage, but Aegeus’s role as Theseus’s father is consistent in the central myth.
A common mix-up is confusing Aegeus with Minos: Aegeus ruled Athens, while Minos ruled Crete and was the Minotaur’s human father.