Tous les combattants
 | Oleg Nagorny | 0-1-0 REC | #7157 |  |
 | Oleg Olenichev | 0-1-0 REC | #5430 |  |
 | Oleg Popov | 7-1-0 REC | #809 | |
 | Oleg Taktarov | 6-2-1 UFC | #1749 | |
 | Oļegs Jemeļjanovs | 0-2-0 REC | #5516 |  |
 | Oleksandr Moisa | 2-1-0 REC | #301 | |
 | Oleksii Polischuck | 4-3-0 REC | #1370 | |
 | Olena Kolesnyk | 4-4-0 REC | #3017 | |
 | Olendet Apouassa Romeo | #7604 |  | |
 | Olga Rubin | 4-3-0 REC | #1684 | |
 | Oli Thompson | 0-2-0 UFC | #4916 |  |
 | Oliver Enkamp | 0-2-0 UFC | #3439 |  |
 | Oliver Tero | 1-1-0 REC | #1179 | |
 | Olivia Hendrickson | 1-0-0 REC | #4756 |  |
 | Olivia Parker | 0-1-0 REC | #4962 | |
 | Olivier Aubin-Mercier | 7-5-0 UFC | #171 |  |
 | Olivier Fleurmon | 1-0-0 REC | #7511 |  |
 | Olivier Murad | 1-0-0 REC | #5269 |  |
 | Olli Santalahti | 2-3-0 REC | #3068 |  |
 | Ollie Sarwa | 4-1-0 REC | #987 | |
 | Olutobi Kalejaiye | 1-1-0 REC | #601 |  |
 | Oluwale Bamgbose | 1-4-0 UFC | #3314 | |
 | Omar Amasha | #7299 |  | |
 | Omar El Bily | 0-1-0 REC | #5518 |  |
 | Omar El Dafrawy | 4-1-0 REC | #1325 | |