A right femur (KCSP-128) from late Pleistocene deposits (ca. 36,210 yr B.P.; Rancholabrean) in Kartchner Caverns State Park, southeastern Arizona, is identified as the larger-than-modern roadrunner, Geococcyx californianus conklingi. This large form is best known from late Pleistocene localities in New Mexico and Nuevo Leon, as well as from assumed mixed late Pleistocene/Holocene deposits from New Mexico, Texas, and Chihuahua. It has never been reported from Arizona. Fossils of the modern-sized form, Geococcyx californianus californianus, have been reported from late Pleistocene localities in California and New Mexico, and from mixed late Pleistocene/Holocene deposits in Chihuahua. Comparisons of the Kartchner Caverns specimen to modern G. c. californianus specimens, and to published data of fossil G. c. californianus and G. c. conklingi, indicate KCSP-128 is relatively larger than the G. c. conklingi data and notably larger than G. c. californianus. KCSP-128 is added to the Rancholabrean record as the first late Pleistocene roadrunner reported from Arizona.