Troilius, in Greek mythology, was the son of Apollo from Hecuba, wife of King Priam of Troy. An oracle prophesied that Troy would not be defeated as long as Troilius reached the age of twenty alive. He and his sister, Polyxena were ambushed and Troilius was killed by Achilles, who later fell in love with Polyxena. During a truce, Achilles was killed visiting her.