In Greek mythology, Troilus is a Trojan prince and one of the many sons of Priam. In medieval and Renaissance versions of the legend of the Trojan War, Troilus falls in love with Cressida, whose father has defected to the Greeks because he can foresee the sack and genocide of Troy. Cressida pledges her love to him, but when she is returned to the Greeks in a hostage exchange, she loses hope, and winds up with the Greek hero Diomedes.

A large, handsome American butterfly (Euphœades troilus, or Papilio troilus). It is black, with yellow marginal spots on the front wings, and blue spots on the rear wings; -- also called troilus butterfly.