Fighters
| Name | Nickname | Ht | Reach | Stance | W | L | D |
|---|---|---|---|---|---|---|---|
| OJ Dominguez | — | — | — | — | 0 | 0 | 0 |
| Oban Elliott | The Welsh Gangster | 6'0" | 72" | orthodox | 4 | 2 | 0 |
| Ode Osbourne | The Jamaican Sensation | 5'7" | 73" | southpaw | 6 | 7 | 0 |
| Olaf Alfonso | — | 6'2" | — | orthodox | 0 | 4 | 0 |
| Oleg Taktarov | The Russian Bear | 6'0" | — | orthodox | 6 | 3 | 1 |
| Oli Thompson | — | 6'1" | 75" | orthodox | 0 | 3 | 0 |
| Oliver Enkamp | — | 6'0" | 77" | switch | 0 | 2 | 0 |
| Olivier Aubin-Mercier | The Canadian Gangster | 5'9" | 70.5" | southpaw | 7 | 5 | 0 |
| Olivier Murad | Warrior of God | 5'10" | 72" | southpaw | 1 | 0 | 0 |
| Oluwale Bamgbose | Holy War Angel | 5'11" | 78" | switch | 1 | 4 | 0 |
| Omar Morales | Venezuelan Fighter | 5'11" | 73" | orthodox | 4 | 4 | 0 |
| Omari Akhmedov | Wolverine | 6'0" | 73" | orthodox | 9 | 5 | 1 |
| Onassis Parungao | — | 5'11" | — | — | 0 | 0 | 0 |
| Orion Cosce | Galaxy | 5'11" | 71" | switch | 2 | 2 | 0 |
| Orlando Wiet | The Gladiator | 5'10" | — | southpaw | 1 | 1 | 0 |
| Oron Kahlon | — | 5'8" | 70" | orthodox | 0 | 1 | 0 |
| Osamu Tachihikari | — | 6'5" | — | orthodox | 0 | 1 | 0 |
| Oscar Cota | Elevation | 6'0" | 72" | orthodox | 0 | 1 | 0 |
| Oskar Piechota | Imadlo | 6'0" | 76" | southpaw | 2 | 3 | 0 |
| Otari Tanzilovi | — | 5'10" | 70" | orthodox | 0 | 1 | 0 |
| Ottman Azaitar | Bulldozer | 5'8" | 71" | switch | 2 | 3 | 0 |
| Oumar Sy | — | 6'4" | 83" | orthodox | 3 | 1 | 0 |
| Ovince Saint Preux | — | 6'3" | 80" | southpaw | 20 | 14 | 0 |
| Ozzy Diaz | — | 6'4" | 79" | orthodox | 1 | 2 | 0 |
OJ Dominguez
0-0-0
Oban Elliott
"The Welsh Gangster"
4-2-0
Ode Osbourne
"The Jamaican Sensation"
6-7-0
Olaf Alfonso
0-4-0
Oleg Taktarov
"The Russian Bear"
6-3-1
Oli Thompson
0-3-0
Oliver Enkamp
0-2-0
Olivier Aubin-Mercier
"The Canadian Gangster"
7-5-0
Olivier Murad
"Warrior of God"
1-0-0
Oluwale Bamgbose
"Holy War Angel"
1-4-0
Omar Morales
"Venezuelan Fighter"
4-4-0
Omari Akhmedov
"Wolverine"
9-5-1
Onassis Parungao
0-0-0
Orion Cosce
"Galaxy"
2-2-0
Orlando Wiet
"The Gladiator"
1-1-0
Oron Kahlon
0-1-0
Osamu Tachihikari
0-1-0
Oscar Cota
"Elevation"
0-1-0
Oskar Piechota
"Imadlo"
2-3-0
Otari Tanzilovi
0-1-0
Ottman Azaitar
"Bulldozer"
2-3-0
Oumar Sy
3-1-0
Ovince Saint Preux
20-14-0
Ozzy Diaz
1-2-0