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The following is a list of characters that appear in the American animated series ThunderCats, its 2011 reboot, ThunderCats Roar, and its related media.

Jaga (voiced by Earl Hammond in the original series, Corey Burton in the 2011 series, Larry Kenney in ThunderCats Roar) is also known as "Jaga the Wise" and is based on the Jaguar. Lion-O regards him as the strongest of the ThunderCats. When he was younger, Jaga was the Lord of the ThunderCats and rescued a young Hachiman from the Jade Dragon. He also served as an adviser and protector of the Lord's family, wielding the Sword of Omens. After Claudus was blinded, Jaga became the guardian of the Eye of Thundera, the Sword of Omens, and the Treasure of Thundera. Prior to Thundera's destruction, Jaga gathered the nobles of the ThunderCats to escort Lion-O and the Eye of Thundera to safety, but did not survive the trip to Third Earth due to volunteering to pilot the damaged ship and died of old age. However, he reappears on Third Earth as a ghost to guide Lion-O, who initially is the only one who can see him. After Jaga's physical body is trapped in another dimension "The Astral Prison", Lion-O travels there to rescue him.

In the 2011 series, Jaga serves as head of Thundera's cleric warriors, possessing knowledge of ancient secrets and having the ability of superhuman speed as well as projecting lightning from his staff. In his prime, he wielded the Sword of Omens in a duel against Ratilla. He sacrifices himself to allow Lion-O and his group to escape, resulting in him being tortured into revealing the location of the Book of Omens to Mumm-Ra. After his soul is sealed in a lantern that Jaga later destroys to save Lion-O, his soul resides within the Book of Omens and becomes Lion-O's guide. When Lion-O encounters Jaga in the entrance to the Spirit World, he tells him of the challenges he must undergo to gain a second chance in life. After he fails the final test, Jaga allows Lion-O to return to the living to save the other ThunderCats, even though it would exile his soul to Limbo by sunrise. However, after he saves his friends, Jaga tells him that it was a test and allows him to remain among the living. Jaga's character was described as being based on "Wisdom".

Lion-O (voiced by Larry Kenney in the original series, Will Friedle and Tara Strong (young) in the 2011 series, Max Mittelman in ThunderCats Roar) is the leader of the ThunderCats and is based on a Lion, who inherited the position of "Lord of the ThunderCats". He wields the Sword of Omens, which possesses various magical abilities, most notably allowing him to see across great distances with "Sight Beyond Sight", and the Claw Shield, a gauntlet that launches grappling lines from its claws. The Sword was forged from the same star as the Sword of Plundarr, with the Eye of Thundera embedded in its hilt once belonging to a beast who Jaga's ancestors imprisoned in a gem after sacrificing themselves to save the Thunderians from him. Though twelve years old at the time of Thundera's destruction, Lion-O aged to adulthood during the trip to Third Earth when his suspension capsule failed to prevent him from aging. Throughout the series, he matures and learns what it takes to be a true leader.