The image of a man with the word "champion" beneath him
A champion was an individual or team who won a game championship or other competition or challenge. A champion could also be someone who was chosen to fight in a duel.
In 2154, Ensign Travis Mayweather and Lieutenant Malcolm Reed played chess aboard the NX-class starship Enterprise while inhabited by Organian observers. Lieutenant Reed claimed that he was the ship's champion and won all the tournaments. (ENT: "Observer Effect")
In 2267, the Vulcan T'Pring, betrothed to Commander Spock of the USS Enterprise, claimed the kal-if-fee and chose Captain James T. Kirk as her champion in a fight to the death with Spock. As an "outworlder," Kirk had the option of declining, in which case a new champion would be selected. After Kirk's apparent death due to the effects of a neural paralyzer, T'Pring explained that she chose him as her champion because had he won, he would not want her and she would be free to be with Stonn instead. If Spock had won, then he would have freed her because she dared to challenge, or if he didn't free her, he would be gone anyway and again she would have Stonn. (TOS: "Amok Time")
In 2370, Miles O'Brien spoke about a game of racquetball between himself and Julian Bashir, where Bashir beat him by only half a step. O'Brien noted that Bashir was a few years younger and didn't have as much experience. Quark drew inspiration as he spoke slogans aloud to himself; "the aging champion... versus the daring challenger" and "Quark's House of Champions." Quark later devised a rematch between O'Brien and Bashir, and he referred to O'Brien as the reigning champion of Starfleet. (DS9: "Rivals")
In 2376, Ensign Harry Kim mentioned he played parrises squares during his time as a cadet at Starfleet Academy, so he knew what it felt like to take an ion mallet to the ribs, and that he was Academy champion three times. (VOY: "Tsunkatse")