P. rex

P. rex may refer to:


 * Papilio rex, the regal swallowtail, a butterfly species found in Africa
 * Pedicularis rex, a plant related to lousewort
 * Percina rex, the Roanoke logperch, a small freshwater fish species found in the Roanoke and Chowan drainages
 * Pseudoeurycea rex, a salamander species found mostly in Guatemala and Mexico