Tous les combattants
 | Oleg Nagorny | 0-1-0 REC | #7457 |  |
 | Oleg Olenichev | 0-1-0 REC | #5823 |  |
 | Oleg Popov | 7-1-0 REC | #1073 | |
 | Oleg Taktarov | 6-2-1 UFC | #1852 | |
 | Oļegs Jemeļjanovs | 0-2-0 REC | #5970 |  |
 | Oleksandr Moisa | 2-1-0 REC | #995 | |
 | Oleksii Polischuck | 4-4-0 REC | #1673 | |
 | Olena Kolesnyk | 4-4-0 REC | #3300 | |
 | Olendet Apouassa Romeo | 0-1-0 REC | #5760 |  |
 | Olga Rubin | 4-3-0 REC | #2114 | |
 | Oli Thompson | 0-2-0 UFC | #5223 |  |
 | Oliver Enkamp | 0-2-0 UFC | #3757 |  |
 | Oliver Tero | 1-1-0 REC | #1896 | |
 | Olivia Hendrickson | 1-0-0 REC | #4952 |  |
 | Olivia Parker | 0-1-0 REC | #5216 | |
 | Olivier Aubin-Mercier | 7-5-0 UFC | #180 |  |
 | Olivier Fleurmon | 1-0-0 REC | #1971 |  |
 | Olivier Murad | 1-0-0 REC | #5439 |  |
 | Olli Santalahti | 2-3-0 REC | #3471 |  |
 | Ollie Sarwa | 5-1-0 REC | #272 | |
 | Ollie Schmid | 0-1-0 UFC | #3171 |  |
 | Olutobi Kalejaiye | 1-1-0 REC | #1389 |  |
 | Oluwale Bamgbose | 1-4-0 UFC | #3578 | |
 | Omar Amasha | #7680 |  | |
 | Omar El Bily | 0-1-0 REC | #5950 |  |