Nidoking is a large, bipedal, purple Pokémon with distinct reptilian features. It has small, narrow eyes, large, spiny ears, fur-like tufts on its cheeks, and a short snout filled with pointed teeth. There is a long, venomous horn on its forehead. It has a gray chest and belly plates, three claws on each hand, rounded spines on its elbows, and a single large nail on each foot. There is a ridge of long spines down its back, and it has a long, powerful tail. This is a male only species; the female counterpart is Nidoqueen.
It is said that Nidoking's tail is capable of toppling a metal transmission tower. Nidoking uses this tail to smash, constrict, or break the bones of its prey and enemies. The tail can be swung to create distance between it and its foes before Nidoking charges. Its steel-like hide adds to its powerful, rampaging charges. Nidoking lives in grasslands, rough terrain, and forests.