Guilmon appears to be relatively small when standing in his normal bent-over bird-like stance, but when standing up-right, he is actually the size of an adult human. Guilmon is a red dragon-like Reptile Digimon with yellow eyes, wing-like ears, a long and strong tail, and carries the black Digital Hazard symbol on his chest. Guilmon is muscular, yet a little slender with big legs, perfect for fast running. On each of his large hands, Guilmon has paws and three fingers with long claws; and on each foot, he has two clawed toes and a claw coming out from the heel. One very indistinct feature of Guilmon is the stripes and triangle patterns on certain parts of his body. On its snout is a black, inverted version of the Zero Unit.
Guilmon's chest is emblazoned with the Digital Hazard symbol.
He is the Red Knight's digimon partner.
Guilmon is a Reptile Digimon, whose name and design may be derived from "Guile". It has an appearance like a dinosaur that still retains its youth. Although it is still a Rookie, its potential as a "Combat Species", something which all Digimon naturally possess, is very high, and it hides the ferocious personality of a carnivorous beast. The mark drawn on its abdomen is called the "Digital Hazard", which is inscribed on those that have the potential to cause massive damage to computer data. However, as long as this ability is used peacefully, it can probably become a being that protects the Digital World.
- Rock Breaker: Destroys rocks with its tough foreclaws.
- Pyro Sphere (Fireball): Spits out a powerful flame shot.
- Kurogane Maru (クレナイマル Kurenai-maru?)
- Rock 'n' Roll Breaker: Drills through its target with its claws.
- Fire Mitt
The name "Guilmon" refers only to the Rookie form of this Digimon. Throughout the series, Guilmon gains the ability to Digivolve into a number of more powerful forms, each with a different name and special attack. However, the Rookie level is his preferred form and the one he spends most of his time in.
Growlmon is the Champion of Guilmon. Growlmon is a Dark Dragon Digimon whose names and design are derived from "Growl". It is called the "Deep-crimson Demon Dragon". The childishness it had when it was Guilmon has vanished, and it digivolved into a wilder, more brutal Digimon. Also, although it is a Virus Digimon, it may even battle for justice depending on how it was raised by its Tamer, because it will be faithfully obedient. Growlmon's roar has the power to shake the solid earth, and before battle it raises its voice to an offensive roar to intimidate the opponent. Its shoulders are adorned with the symbol of the Digital Hazard, and the DigiCode on its stripes reads (デジタルモンスター Dejitaru Monsutā?, lit. "Digital Monster").
WarGrowlmon X is the Ultimate form of Guilmon. WarGrowlmon is an Android Digimon whose Japanese name and design are derived from "Great (μεγαλο Megalo?) Growlmon", and whose English name is derived from "War Growlmon". As its name suggests, it body has grown gigantic, and its upper body has been metallized with the strongest metal, "Chrome Digizoid". It is able to take flight with the two vernier attached to both of its shoulders, so it is possible for it to perform both anti-air and anti-ground attacks. In order to suppress its rampaging due to excess power, a restraining tool similar to a bit is attached to its jaw section. Also, since the "Assault Balancer" extending like a cable from its back section is extensible, it can be used to impale the opponent. It has the "Pendulum Blades" equipped to both of its arms. Its harness is adorned with the symbol of the Digital Hazard, and the DigiCode on its stripes reads (デジタルモンスター Dejitaru Monsutā?, lit. "Digital Monster"). WarGrowlmon X is a WarGrowlmon who has been affected by the X-Antibody.