Voiced by Mona Marshall
Terriermon first matrix digivolved to Rapidmon during the battle with Pajiramon, when Henry used a blue card from Shibumi. Rapidmon gained the upper hand on Pajiramon, eventually destroying her and Vajramon, although Vajramon returned.
When the tamers figured out how to turn cards into blue cards and matrix digivolve their Digimon at will, Rapidmon fought Vikaralamon alongside WarGrowlmon and Taomon. Rapidmon, Taomon, and Vikaralamon were nearly killed when Yamaki activated Juggernaut, but when Makuramon destroyed the vortex, the battle resumed. Rapidmon and Taomon stopped Vikaralamon's attacks and WarGrowlmon destroyed him.
Terriermon later digivolved to Rapidmon to fight Beelzemon, but was at a disadvantage, and stepped out of the fight when Guilmon dark digivolved to Megidramon to fight him. Rapidmon re-entered the fight when Beelzemon destroyed Makuramon, but Beelzemon used Makuramon's Primal Orb in an attempt to absorb him and Taomon. Henry and Rika saved them with the Alias card, but although they retained the ability to matrix digivolve, their ultimate data was absorbed, having the same effect on Beelzemon as if he destroyed them.
Later, Rapidmon fought alongside WarGrowlmon and Taomon against Zhuqiaomon, but due to an injury Caturamon inflicted on him as Terriermon he seemed to slowly be dying, but eventually biomerged with Henry into MegaGargomon.
Terriermon later took this form to fight the D-Reaper agent, Pendulum Feet. Although he, WarGrowlmon, and Taomon successfully destroyed it with Beelzemon's help, they were no match for Creep Hands, until Dobermon gave them the ability to biomerge on Earth. For the majority of the remaining battles, Terriermon biomerged with Henry.
- Tri Beam - Shoots a powerful triangle-shaped laser
- Homing Blast - Shoots a missile
- Rapid Fire - Shoots a barrage of missiles
- In Beelzemon's Big Day, Rapidmon sounds like he's saying "Renamon" when he digivolves, when he should be saying "Rapidmon"
- In the first Digimon movie, Terriermon Golden Armor Digivolves to a Mega form of Rapidmon, who has a deeper voice and gold armor, while in Digimon Tamers, Rapidmon is green rather than gold, is an Ultimate level, and has the same voice as Terriermon and Gargomon