Nidoking is a large, bipedal, purple mammalian Pokémon with distinct reptilian features. It has 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 and a ridge of spines down its back. Gray plates cover its chest and belly, and there is a gray, rounded spine on each elbow. Each hand has three claws, while each foot has only a single hoof-like nail. It has a long, powerful tail. Nidoking is a male-only species.
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 also be swung to create distance between it and its foes before Nidoking charges. Its steel-like hide adds to its powerful, rampaging charges. Nidoking's horn is powerful enough to crush diamonds. Nidoking is known to be very proud of its own strength. When Nidoking goes on a rampage, it becomes impossible to control. Only a Nidoqueen that it has lived with for a long time can calm it down from its rampages. As shown in the manga, Nidoking has strong acid within its claws. Being the result of evolution via an Evolution stone, Nidoking is rarely found in the wild, though they can be found in savannas and plains.
In The Battle of the Badge, Gary Oak used a Nidoking to battle Giovanni's Golem during their Gym battle. Nidoking was revealed to have tremendous power as he managed to Tackle Golem head-on, launch it across the battlefield, and defeat it in one hit. However, when Giovanni used Mewtwo, Nidoking was no match and was defeated easily. This battle was shown again from Mewtwo's perspective in Mewtwo Strikes Back. In The Fourth Round Rumble, Nidoking battled Melissa's Golem but was defeated easily. He reappeared again in Mewtwo Strikes Back—Evolution, a remake of Mewtwo Strikes Back, where he played the same role.
In In the Pink, a pink Nidoking was a resident of Pinkan Island. He attacked Jessie and James as they were attempting to capture a pink Nidoran couple. He was eventually subdued by Officer Jenny.
In Showdown at the Oak Corral, a Nidoking tried to mate with Cassidy, who was in a Nidoqueen costume at the time.
In The Bicker the Better, Oscar has a Nidoking, while his girlfriend Andi had a Nidoqueen. They had a Double Battle with Ash and May, and due to Oscar and Andi's communication with each other, they were able to defeat Ash and May with relative ease.
In A Pyramiding Rage!, Paul used a Nidoking to battle Brandon's Registeel. Although Nidoking was powerful and versatile, Registeel was still able to hold its own and eventually brought down Nidoking.
In the original timeline of Arceus and the Jewel of Life, two Nidoking were used by Damos, who was under Hypnosis, to attack Arceus with Shock Wave. When Ash and his friends traveled to the past to prevent this, Marcus, the one responsible for hypnotizing Damos, managed to use the Nidoking again to attack Arceus.
In Mystery on a Deserted Island!, a Nidoking was a resident of the Deserted Island. He was first seen chasing a trio of Eevee before being intimidated into leaving by Pikachu's Iron Tail. He later attacked Team Rocket but was defeated by them.
In a flashback in Enter Pikachu!, a young Goh and Chloe saw a Nidoking battling a Mew that was copying its moves. He reappeared in flashbacks in Mind-Boggling Dynamax! and Time After Time!.
In A Chansey Operation, a sick Nidoking was seen.
A Nidoking appeared in Meowth Rules!, under the ownership of the Golden Island villagers.
In The Power of One, a Nidoking sensed the disturbance caused by Lawrence III.
A Nidoking appeared in a fantasy in The Rivalry Revival.
In Wired for Battle!, a Nidoking was in Muramasa's dojo.
In Ring Masters, a Nidoking competed in Rikishii Town's Sumo Conference.
Multiple Nidoking appeared in Celebi: The Voice of the Forest.
In a flashback in Throwing in the Noctowl, a Nidoking was defeated by Wings Alexander's then-Hoothoot.
In As Cold as Pryce, Pryce remembered a Trainer's Nidoking as one of the Pokémon that fought his Piloswine.
In A Claim to Flame!, a female Trainer's Nidoking participated in a qualifying match for the Silver Conference.
In Saved by the Beldum, a Trainer's Nidoking was seen during the Ever Grande Conference.
In Lucario and the Mystery of Mew, multiple Nidoking were part of the feuding armies that were eventually placated by Sir Aaron in the past.
In Odd Pokémon Out!, a Nidoking was a resident of Camomile Island.
A Coordinator's Nidoking appeared in Settling a Not-So-Old Score!.
In Pokémon Ranger and the Kidnapped Riolu! (Part 2), J's client's henchmen used a Nidoking to attack Dawn, Brock, Officer Jenny, and Solana.
In Historical Mystery Tour!, Ash encountered a Nidoking in Xatu's Forest.
A Nidoking appeared in the opening sequence of Zoroark: Master of Illusions.
A Nidoking appeared in Cilan's demonstration in Mystery on a Deserted Island!, where he evolved from a Nidoran♂.
A soldier's Nidoking appeared in a flashback in The Legend of X, Y, and Z!.
In I Choose You!, a Nidoking was under the control of Marshadow.
||Nidoking, the Drill Pokémon. Nidoking swings its large tail about to create distance, then charges in with the full force of its body behind it.
||Nidoking, the Drill Pokémon. One swing of its mighty tail can snap a telephone pole as if it were nothing but a matchstick.
In File 1: Red, a Nidoking was one of the Pokémon seen in Professor Oak's introduction.