Rhydon is a large, gray, bipedal Pokémon with features similar to both dinosaurs and rhinoceroses. It has narrow, red eyes and two fangs in its upper jaw. On the tip of its snout is a cream-colored horn, which is smaller on a female than a male. There are several other spikes and projections on its head: on top is spike that curves forward, two triangular points resembling ears on the sides, a wide, wavy crest under each ear, and spiky ridges on each cheek. It has a cream-colored abdomen divided into strips by thin divots. A rocky plate on its chest slightly overlaps its abdomen. There is a row of spikes down its back, and has a long tail with thin, black stripes.
Rhydon is a physically powerful Pokémon. It is recorded as being able to topple buildings with a sweeping blow of its tail, and its horn is able to bore through solid rock and shatter diamonds. Its armor-like hide protects it from heat and physical blows. It is stated to be capable of passing unscathed through streams of magma and withstanding a direct blow from a cannonball without being harmed. However, because of this tough hide, it is insensitive. Despite its well-developed brain, it can be forgetful. Rhydon lives in rough terrain.
A Rhydon appeared in Riddle Me This, under the ownership of Blaine. Blaine used Rhydon against Ash during a Gymbattle. It briefly battled Charizard who then refused to battle. While normally tough against Electric attacks, Rhydon was defeated when Pikachu struck Rhydon's horn, which acted like a lightning rod. It reappeared in a flashback in Volcanic Panic.
A Rhydon appeared in Right On, Rhydon!, where it was unique for its strength and its ability to know Surf. As a result, Pietra sought to catch it, but she needed a surfing Pokémon to accomplish this task. Pietra eventually caught Rhydon after rescuing it from Team Rocket.
A Rhydon appeared in Bibarel Gnaws Best!, under the ownership of the head engineer. It was used in order to drill out rocks for the bridge, but the Drill Pokémon was quickly attacked and defeated by a Bibarel. When Bibarel was cornered, Ash's Pikachu used Iron Tail to finish Rhydon off for good.
Blue owns a Rhydon, which appeared in The Challenger. He used it during his Indigo League battle against Agatha, where it was seen taking on her Arbok and Gengar. It managed to defeat Arbok, but it is unclear if it won against Gengar as well, for the outcome of that battle was never shown onscreen. Whatever the case, Blue eventually managed to defeat Agatha, allowing him to progress to Lance's room.
Two soldiers' Rhydon appeared in The Redemption, during a fantasy of a story from the past. They were seen petrified after the ultimate weapon was used by AZ to end the great war of Kalos 3,000 years previously.
In How Do You Do, Sudowoodo?, Gold encounters a wild Rhydon during his race with Whitney. It was hunting down a Sudowoodo, and kidnapped Whitney when she interfered with her Miltank, breaking her arm in the process. Gold tells Sudowoodo to stand up for itself and, with assistance from his billiard cue, helps Sudowoodo defeat the Rhydon with a strong punch to the gut.
In Rock, Paper...Scizor, Bluecatches a Rhydon outside the Viridian Gym. He uses him to defeat Chuck in Heckled by Hitmontop, as well as Orm in Don't Doubt Deoxys. Near the end of the FireRed and LeafGreen saga, Blue remarks on a footnote Giovanni included in his handbook: Rhydon possibly possessed a stronger form. This is a reference to Rhydon's new evolved form, Rhyperior, an evolution that succeeded in occurring thanks to Silver's knowledge of Pokémon trading, resulting in the same Rhydon, as Rhyperior, being on hand with him until being returned to Blue later on.
Evolves from Rhyhorn when its Attack is 108 or higher Evolves into Rhyperior after knocking out a Warrior's Pokémon in a manner that allows recruitment, while its own Warrior is equipped with a Protector
Ash's Pikachu fought Blaine's Rhydon in the anime and defeated it, despite it being a Ground-type immune to Electric attacks. Rhydon's horn also serves as a lightning rod which negates electric attacks as of the rules for the Pokémon effect. Since then, that battle has been brought up frequently in comparisons between the games and anime and has spawned the popular (albeit misquoted) Pokémon Internet meme, "Pikachu! Aim for the horn!"
Rhydon may be a combination of rhinoceros and don. Rhy may also derive from the igneous rock called rhyolite, alluding to Rhydon's Ground/Rock type combination. Don, from the Latin dominus, may emphasize Rhydon's being the final evolution of its line (pre-Generation IV), as it is a title akin to lord in several Romance languages; -odon, ultimately from ὀδούς, the ancient Greek word for tooth, is a suffix commonly used in dinosaur names, and so Rhydon's name could be a reference to those prehistoric creatures as well.
Sidon is a combination of 犀 sai (rhinoceros) and don.