Volcanion is a primarily maroon, quadruped Pokémon with blue and yellow markings. It has large, pointed ears with blue insides and bright blue eyes. Additionally, it has bushy yellow eyebrows and a yellow mandible. There are spike-protrusions on each cheek that extend downward over its lower jaw. Volcanion's body has two oval segments separated by a thinner, blue portion. The front portion the body is larger and has two large, arm-like cannons on the back. These cannons are usually held together, forming a ring. Each cannon is separated into three segments by bright blue lines, and each segment has a single blue dot and short, blunt growth. The topmost segments also have four small, yellow bumps around the end. On its chest are four yellow, diamond-shaped markings. There is a thin, yellow band around each of its leg joints. The upper portion of its legs is black and smaller than the large, red lower portion. Each ankle has a short, blunt growth, while each foot has three yellow claws. Volcanion has a short, tapering tail with a blue stripe on top.
Volcanion has a unique organ capable of turning water vapor around it into hot steam in an instant. It can expel steam of superbly high pressure and has the ability to blow away mountains, and is worshiped in southern parts of Kalos for creating the plain in that part of Kalos. As shown in Volcanion and the Mechanical Marvel, Volcanion is able to run out of water; when it does, a sound similar to a starting bell in boxing is heard, the lines and dots on its cannons become red, and it is unable to use any Water-type move until it refills its water supply from any source of water.
Volcanion appears to be based on the Ryukyuanshisa, or komainu, mythical creatures inspired by lions, tigers, and dogs. Statues of them in pairs are used as guardians that invite good spirits and repel evil ones. Its mechanical appearance and cannon-like "arms" may also draw inspiration from tanks. Its type combination and signature move may refer to geysers. Its ability to fly using its cannon-like "arms" may also draw inspiration from a steam engine.
Volcanion may be a combination of volcano and lion. It may also include canyon, referring to its ability to break large landmasses. "Canion" may also be a corruption of cannon.