| First | Last | Nickname | Ht. | Wt. | Reach | Stance | W | L | D | Belt |
|---|---|---|---|---|---|---|---|---|---|---|
| Michal | Oleksiejczuk | Lord | 6' 0" | 205 lbs. | 74.0" | Southpaw | 14 | 4 | 0 | |
| Rafaello | Oliveira | Tractor | 5' 8" | 155 lbs. | 71.0" | Orthodox | 17 | 8 | 0 | |
| Charles | Oliveira | Do Bronx | 5' 10" | 155 lbs. | 74.0" | Orthodox | 30 | 8 | 0 | |
| Jorge | Oliveira | 6' 1" | 205 lbs. | -- | 5 | 3 | 1 | |||
| Ednaldo | Oliveira | Lula | 6' 5" | 205 lbs. | -- | Orthodox | 17 | 3 | 1 | |
| Alex | Oliveira | Cowboy | 5' 11" | 170 lbs. | 76.0" | Orthodox | 22 | 9 | 1 | |
| Bruno | Oliveira | 6' 4" | 205 lbs. | 80.0" | Orthodox | 8 | 2 | 0 | ||
| Wendell | Oliveira Marques | The Machine | 5' 10" | 170 lbs. | -- | Orthodox | 29 | 10 | 0 | |
| Felipe | Olivieri | 5' 9" | 155 lbs. | -- | Orthodox | 14 | 5 | 0 | ||
| Andy | Ologun | 6' 0" | 154 lbs. | -- | Orthodox | 3 | 1 | 0 | ||
| Shana | Olsen | Rock Solid | 5' 7" | 145 lbs. | -- | 5 | 2 | 0 | ||
| Casey | Olson | The Underdog | 5' 7" | 145 lbs. | -- | Orthodox | 14 | 5 | 0 | |
| Dennis | Olson | 6' 0" | 170 lbs. | -- | 14 | 11 | 0 | |||
| Cameron | Olson | Cap'n Crunch | 6' 1" | 205 lbs. | 75.0" | Orthodox | 7 | 3 | 0 | |
| Alan | Omer | 5' 10" | 145 lbs. | -- | Orthodox | 20 | 5 | 0 | ||
| Daniel | Omielanczuk | 6' 0" | 247 lbs. | 74.0" | Southpaw | 19 | 8 | 1 | ||
| Michihiro | Omigawa | 5' 6" | 145 lbs. | 68.0" | Orthodox | 17 | 14 | 1 | ||
| Charlie | Ontiveros | American Bad Boy | 6' 2" | 185 lbs. | 78.0" | Switch | 11 | 7 | 0 | |
| Chibwikem | Onyenegecha | 6' 3" | 185 lbs. | -- | Orthodox | 5 | 0 | 0 | ||
| Sam | Oropeza | 6' 2" | 170 lbs. | -- | 13 | 3 | 0 | |||
| Brian | Ortega | T-City | 5' 8" | 145 lbs. | 69.0" | Switch | 15 | 1 | 0 | |
| Tito | Ortiz | The People's Champ | 6' 3" | 205 lbs. | 74.0" | Orthodox | 19 | 12 | 1 | |
| Jorge | Ortiz | The Naked Man | 6' 0" | 185 lbs. | -- | Orthodox | 18 | 9 | 1 | |
| Dustin | Ortiz | 5' 5" | 125 lbs. | 65.0" | Orthodox | 19 | 8 | 0 |