Tous les combattants
 | Oleg Popov | 7-1-0 REC | #942 |  |
 | Oleg Taktarov | 6-2-1 UFC | #1770 | |
 | Oļegs Jemeļjanovs | 0-2-0 REC | #5683 |  |
 | Oleksandr Moisa | 2-1-0 REC | #614 |  |
 | Oleksii Polischuck | 4-4-0 REC | #1430 | |
 | Olena Kolesnyk | 4-4-0 REC | #3175 | |
 | Olendet Apouassa Romeo | 0-1-0 REC | #5488 |  |
 | Olga Rubin | 4-3-0 REC | #1887 | |
 | Oli Thompson | 0-2-0 UFC | #5102 |  |
 | Oliver Enkamp | 0-2-0 UFC | #3588 |  |
 | Oliver Tero | 1-1-0 REC | #1542 | |
 | Olivia Hendrickson | 1-0-0 REC | #4940 |  |
 | Olivia Parker | 0-1-0 REC | #5026 | |
 | Olivier Aubin-Mercier | 7-5-0 UFC | #171 |  |
 | Olivier Fleurmon | 1-0-0 REC | #1687 |  |
 | Olivier Murad | 1-0-0 REC | #5468 |  |
 | Olli Santalahti | 2-3-0 REC | #3285 |  |
 | Ollie Sarwa | 4-1-0 REC | #1289 | |
 | Ollie Schmid | 0-1-0 UFC | #3168 |  |
 | Olutobi Kalejaiye | 1-1-0 REC | #1010 |  |
 | Oluwale Bamgbose | 1-4-0 UFC | #3422 | |
 | Omar Amasha | #7519 |  | |
 | Omar El Bily | 0-1-0 REC | #5663 |  |
 | Omar El Dafrawy | 5-1-0 REC | #382 | |
 | Omar Hussein | 0-2-0 REC | #3642 |  |