Groudon is a massive, bipedal, dinosaur-like creature covered in red, segmented plates of thick skin that act as armor. It has a gray underside and large white spikes that run along the sides of its head, body, and tail. It has four claws on each hand, four dozer-like blades on the end of its large tail, and three claws on each foot with grey markings under its feet. It also has blue stripes inside the seams of its armor plating which can only be seen when Groudon is glowing with power.
As Primal Groudon, its appearance is similar to Groudon, but larger in size. Its skin color changes from dark red to deep crimson with its underside, spikes, and teeth turning black. The blades on its tail are more separated from one another. The Ω symbol is now shown on its arms. Its eyes, the inside of its mouth, and the now-enlarged openings between its armor plating glow bright yellow, and its irises are now red. The energy that fills Primal Groudon pours forth as magma, and it burns with such an extreme temperature that its body is always shimmering with the haze of its heat. In the anime, Primal Groudon is said to create new land with every step it takes.
Groudon is an immensely powerful Pokémon, having the ability to summon intense droughts and cause volcanic eruptions. The droughts it can cause allow it to evaporate water, while the volcanic eruptions it can summon enable it to create land. It sleeps underground in large magma chambers. If it encounters its rival, Kyogre, they will engage in a cataclysmic battle. Groudon is the only known Pokémon capable of learning the move Precipice Blades.