Leomon is Jeri's partner. He is a Champion level Digimon.
He has the appearance of a humanoid lion.
Leomon initially only knew fighting in the digital world, much like Terriermon and Renamon, but would only fight for good instead of evil. At one point he arrived on Earth and saved Jeri and Calumon from Kumbhiramon. Jeri became convinced that Leomon was his tamer and chased him around. When Kumbhiramon returned, it was established that Jeri was not his tamer. After destroying Kumbhiramon, Leomon walked away.
He later returned to fight Makuramon, who injured him by throwing pins at him. However Jeri received a digivice, becoming Leomon's tamer and healing his injuries. She had him talk to her father, Mr. Katou, before leaving for the Digital World.
While in the digital world, Leomon and Renamon knew the most about the digital world so they explained the many things about it to the others. When Rika, Renamon, Kazu, and Kenta were separated from the group by a data stream, they searched for them and came across the Forgotten Village where they fought the motorcycle Behemoth. When it controlled Guilmon to ride him, Leomon knocked him off with his sword to release him from its control and send the motorcycle falling into the lava.
After the tamers reunited, Takato, Henry, and Terriermon were separated again by Caturamon. While searching for them, they came across the forest of Gekomon who were enslaved by Orochimon, who kidnapped Jeri. Leomon fought alongside Guilmon and Renamon against him, and in the end Jeri used a LadyDevimon card on Leomon, who used Darkness Wave to destroy Orochimon.
While continuing their search, Jeri wondered whether Leomon was disappointed that he got her as his tamer. Leomon said that Jeri has a lion's heart.
Eventually a data stream controlled by Caturamon reunited them with Takato, Henry, and Rapidmon, who were fighting Beelzemon. As Beelzemon was about to kill Kyubimon, Leomon stopped him and tried to tell him that he was being used. Beelzemon ignored him to Leomon punched him and told him that to have power is not to be strong. Beelzemon impaled Leomon with his hand, destroying him and absorbing his data.
Leomon's death sent Jeri into a depression which the D-Reaper took advantage of. However, Leomon's spirit returned from the other side twice; The first was when Beelzemon, trying to rescue Jeri from the D-Reaper, called upon the data he absorbed from Leomon to use his attack, during which Leomon's spirit seemed to appear and give him additional power. The second was when Jeri finally fought back against the D-Reaper, and Leomon's spirit briefly appeared inside her digivice and blasted a hole in the D-Reaper's head.
- Fist of the Beast King - Shoots a fireball from his fist
Leomon also attacks with a sword
- Killing Leomon seems to be tradition for seasons of Digimon.
- Leomon is one of two characters to return as a ghost, the other being Alice.
- Leomon's last words in the original episode was "so this is my fate". They were changed to more encouraging ones.