Combattants Etats-Unis
| 1901 |  | Noufel El Kasri | #7677 |  | |
| 1902 |  | Nyle Bartling | 0-1-0 REC | #6291 | |
| 1903 |  | Ode Osbourne | 5-7-0, 1NC UFC | #950 | |
| 1904 |  | Olivia Hendrickson | 1-0-0 REC | #4973 | |
| 1905 |  | Olivia Parker | 0-1-0 REC | #5239 | |
| 1906 |  | Oluwale Bamgbose | 1-4-0 UFC | #3585 | |
| 1907 |  | Omoyele Gonzalez | 0-1-0 REC | #5782 | |
| 1908 |  | Orion Cosce | 1-2-0 UFC | #3979 | |
| 1909 |  | Orlando Sanders | 0-1-0 REC | #7447 | |
| 1910 |  | Oscar Jurado Sanchez | 1-0-0 REC | #1199 | |
| 1911 |  | Oseyiomon Oiyemhonlan | 1-2-0 REC | #4656 | |
| 1912 |  | Ovince St. Preux | 15-13-0 UFC | #273 | |
| 1913 |  | Ozzy Diaz | 1-2-0 UFC | #1387 | |
| 1914 |  | Pablo Garza | 3-3-0 UFC | #3169 | |
| 1915 |  | Paige VanZant | 5-4-0 UFC | #1733 | |
| 1916 |  | Pam Sorenson | 0-2-0 REC | #5367 | |
| 1917 |  | Paris Moran | #8039 | | |
| 1918 |  | Parker Porter | 4-4-0 UFC | #2409 | |
| 1919 |  | Pat Audinwood | 0-2-0 UFC | #5583 | |
| 1920 |  | Pat Barry | 5-7-0 UFC | #2024 | |
| 1921 |  | Pat Downey | 1-1-0 REC | #4558 | |
| 1922 |  | Pat Healy | 0-5-0, 1NC UFC | #2963 | |
| 1923 |  | Pat Miletich | 8-2-0 UFC | #326 | |
| 1924 |  | Pat Sabatini | 9-2-0 UFC | #231 | |
| 1925 |  | Pat Schilling | 0-2-0 UFC | #4253 | |