Combattants Etats-Unis
| 1926 |  | Olivia Hendrickson | 1-0-0 REC | #5051 |  |
| 1927 |  | Olivia Parker | 0-1-0 REC | #5241 | |
| 1928 |  | Oluwale Bamgbose | 1-4-0 UFC | #3651 | |
| 1929 |  | Omoyele Gonzalez | 0-1-0 REC | #5994 | |
| 1930 |  | Orion Cosce | 1-2-0 UFC | #3895 | |
| 1931 |  | Orlando Sanders | 0-1-0 REC | #7589 | |
| 1932 |  | Oscar Jurado Sanchez | 2-0-0 REC | #385 | |
| 1933 |  | Oseyiomon Oiyemhonlan | 1-2-0 REC | #4815 | |
| 1934 |  | Ovince St. Preux | 15-13-0 UFC | #286 | |
| 1935 |  | Ozzy Diaz | 1-2-0 UFC | #1438 | |
| 1936 |  | Pablo Garza | 3-3-0 UFC | #3186 | |
| 1937 |  | Paige VanZant | 5-4-0 UFC | #1771 | |
| 1938 |  | Pam Sorenson | 0-2-0 REC | #5460 | |
| 1939 |  | Paris Moran | #8099 | | |
| 1940 |  | Parker Porter | 4-4-0 UFC | #2456 | |
| 1941 |  | Pat Audinwood | 0-2-0 UFC | #5594 | |
| 1942 |  | Pat Barry | 5-7-0 UFC | #2060 | |
| 1943 |  | Pat Downey | 1-1-0 REC | #4610 | |
| 1944 |  | Pat Healy | 0-5-0, 1NC UFC | #2941 | |
| 1945 |  | Pat Miletich | 8-2-0 UFC | #345 | |
| 1946 |  | Pat Sabatini | 9-2-0 UFC | #310 | |
| 1947 |  | Pat Schilling | 0-2-0 UFC | #4296 | |
| 1948 |  | Patchy Mix | 0-2-0 UFC | #1281 | |
| 1949 |  | Patrick Brady | 0-1-0 REC | #7641 | |
| 1950 |  | Patrick Cornett | 0-1-0 REC | #6937 | |