- Voice actor: Unshō Ishizuka (both English and Japanese)
Steelix resemble giant iron snakes. They are a reflective, silvery gray, which reflects the sunlight making them shine slightly. They are about 30 feet long. Their body is made up of rock-like sections, some of which have massive rock spikes coming out of them. They have a massive head mainly made up of their jaw. The jaw is large and wide with sets of large square teeth inside. Along their bottom jaw are a pair of ridges (varies with gender). Their eye sockets are slightly set in, giving them good eye protection. Underneath their bottom jaw and chin, on the underside of the jaw, there are small square domes. Their heads have two long ridges going from the eyes up to the top of their heads. Their jaws also have massive ridges where they meet their skull. Steelix's height is 30'02" and its weight is 881.8 lbs. The rock portions on their body start at the back of their head. There are three slightly larger sections that have the massive rock-like spikes coming out of them. The tail ends in a long sharp point, but with a blunt tip. Steelix's rock-like sections don't look perfect and can easily be mistaken for rocks, for they have many chips and scrapes all along them from fights and tunneling.
A male Steelix has two pairs of sharp ridges on each side of its bottom jaw, one big one and one slightly smaller one. A female Steelix has only one pair of ridges on either side of its bottom jaw, each the approximate size of the male's larger ridges.
Steelix are rather rash and often charge into situations without thinking about the consequences of their actions. Often if they are disturbed they will attack anyone rather than the actual person responsible for disturbing them. They also often prone to being a bit vain and in some cases a bully to other Pokémon that happen to live in the area they are living in. This could be from evolving from Onix and realizing how powerful they have become and letting this knowledge go to their heads, as Onix are usually more peaceful than Steelix. Steelix don't give up until they are beaten. Often they are adamant about their choice of action. Steelix like to burrow underground and prefer to live inside mountains or on mountains, or even caves.
Although Steelix require an item to evolve from Onix, they can be sometimes be found in the wild, where they populate deep caverns, tunnels, and an old temple in the Sinnoh region and a cliffside cave in the Johto region. As they live far underground, miles from the surface, they don't often surface above ground unless provoked. It is said that when an earthquake happens, multiple Steelix are battling far below the surface.
- Main article: Pokémon food
From Steelix's Pokédex entries, it can be presumed that Steelix eat soil and boulders.
Steelix first appeared as one of Jasmine's Pokémon in Nerves of Steelix!. Jasmine first used Steelix to help Ash stop Team Rocket and Dr. Eggman from stealing Pikachu. Then, during the Gym battle, Ash's Cyndaquil managed to defeat it, winning Ash the Mineral Badge.
A Steelix was one of the three Pokémon used by Attila and Hun of Team Rocket in The Legend of Thunder!. In All Torkoal, No Play, a Steelix from Steel Valley was scaring the wits out of a wild Torkoal that would soon belong to Ash. Team Rocket accidentally stuck three shovels into the head of an underground Steelix while digging a pitfall trap in Faced with Steelix Determination. It went on to terrorize a village of Bidoof until the shovels were removed through the combined efforts of multiple Bidoof, Ash's Staravia, and his Pikachu. In Dealing With Defensive Types!, a Steelix belonging to Byron was used in the Gym battle against Ash. It put up a tough fight, defeating Ash's Buizel, despite its type advantage and then fought against Ash's Chimchar. Despite its exhaustion from its earlier battle, Chimchar was able to defeat Steelix after a prolonged battle. Steelix appeared in Steeling Peace of Mind! and Saving the World From Ruins! where it was one of the Steel-type Pokémon on Iron Island that had gone crazy due to Team Galactic.
Steelix, Iron Snake Pokémon. The evolved form of Onix. Strengthened and compressed under high pressure and intense heat of living underground, Steelix's body is stronger than steel and harder than metal and diamonds.