Papilio rex, the regal swallowtail or king papilio, is a butterfly of the family Papilionidae. It is found in Africa. The Kenyan forms mimic Tirumala formosa, the forest monarch butterfly. The larvae feed on Teclea tricocarpa, Teclea stuhlmanni, Calodendrum, Citrus, Clausena, Fagara and Toddalia species.