Tous les combattants
 | Oscar Jurado Sanchez | 2-0-0 REC | #385 |  |
 | Oscar Mendez | 0-1-0 REC | #5140 |  |
 | Oscar Miguel | #7905 |  | |
 | Oscar Ownsworth | 2-3-0 REC | #746 |  |
 | Oscar Ravello | #8059 | | |
 | Oseas Cruz Furtado | 0-1-0 REC | #7954 |  |
 | Oseyiomon Oiyemhonlan | 1-2-0 REC | #4815 | |
 | Osimkhon Rakhmonov | 3-1-0 REC | #390 |  |
 | Oskar Piechota | 2-3-0, 1NC UFC | #3802 |  |
 | Oskar Stachura | 1-1-0 REC | #736 | |
 | Oskar Staszczak | 1-0-0 REC | #2549 | |
 | Oskar Szczepaniak | 4-2-0 REC | #2994 | |
 | Osman Minbatirov | 1-1-0 REC | #6023 |  |
 | Osvaldo Benedito | 0-1-0 REC | #5214 |  |
 | Otabek Rajabov | 1-0-0 REC | #3551 | |
 | Otar Tanzilov | 0-1-0 REC | #4906 |  |
 | Otari Tanzilovi | 0-1-0 UFC | #3851 | |
 | Otgonbaatar Boldbaatar | 0-1-0 REC | #5722 |  |
 | Oton Jasse | 0-3-0 REC | #4363 | |
 | Ottman Azaitar | 2-3-0 UFC | #1879 |  |
 | Otto Rodrigues | 1-1-0 REC | #6631 | |
 | Oualy Tandia | 1-0-0 REC | #844 |  |
 | Oumar Kane | 1-0-0 REC | #3025 |  |
 | Oumar Sy | 3-2-0 UFC | #353 | |
 | Ourouzmag Magkeyev | 0-1-0 REC | #4409 | |