| Fighter | Record | Last Bout |
|---|---|---|
| Juan Adams | 5-3-0 | 2020-02-08 |
| Juan Diaz | 16-1-1 | 2026-05-16 |
| Juan Espino | 11-2-0 | 2021-04-17 |
| Juan Manuel Puig | 11-4-0 | 2014-11-22 |
| Juancamilo Ronderos | 4-2-0 | 2023-02-18 |
| Jules Bruchez | 1-2-0 | 2008-12-13 |
| Julia Avila | 9-4-0 | 2025-02-15 |
| Julia Polastri | 15-6-0 | 2026-08-29 |
| Julian Erosa | 31-14-0 | 2026-03-28 |
| Julian Marquez | 9-6-0 | 2025-03-01 |
| Julian Sanchez | 0-1-0 | 1996-09-20 |
| Juliana Lima | 9-5-0 | 2018-01-27 |
| Juliana Miller | 6-4-0 | 2026-08-08 |
| Julianna Pena | 13-6-0 | 2025-06-07 |
| Julie Kedzie | 16-13-0 | 2013-12-06 |
| Julien Leblanc | 10-3-0 | 2026-10-17 |
| Julija Stoliarenko | 11-10-2 | 2025-08-09 |
| Julio Arce | 19-6-0 | 2024-03-30 |
| Julio Paulino | 23-5-0 | 2010-09-25 |
| Julius Walker | 7-3-0 | 2026-06-27 |
| Jumabieke Tuerxun | 19-4-1 | 2014-11-07 |
| Junie Browning | 5-6-0 | 2009-04-01 |
| Junior Albini | 14-6-0 | 2019-06-29 |
| Junior Assuncao | 16-6-0 | 2011-12-30 |
| Junior Dos Santos | 21-9-0 | 2020-12-12 |
| Junior Tafa | 7-6-0 | 2026-06-06 |
| JunYong Park | 19-7-0 | 2025-10-25 |
| Jussier Formiga | 23-8-0 | 2020-06-06 |
| Justin Buchholz | 15-10-0 | 2010-02-06 |
| Justin Edwards | 9-5-0 | 2015-06-06 |
| Justin Eilers | 19-7-1 | 2006-02-04 |
| Justin Frazier | 10-3-0 | 2018-11-30 |
| Justin Gaethje | 28-5-0 | 2026-06-14 |
| Justin James | 13-7-0 | 2006-10-14 |
| Justin Jaynes | 16-8-0 | 2021-06-26 |
| Justin Jones | 9-2-0 | 2015-04-04 |
| Justin Lawrence | 10-4-0 | 2013-04-13 |
| Justin Ledet | 9-4-0 (1 NC) | 2020-10-31 |
| Justin Levens | 10-7-0 | 2006-06-28 |
| Justin Martin | 4-3-0 | 1997-02-07 |
| Justin McCully | 11-5-2 | 2009-08-29 |
| Justin Salas | 12-7-0 | 2016-03-05 |
| Justin Scoggins | 11-5-0 | 2018-07-14 |
| Justin Tafa | 7-5-0 (1 NC) | 2025-02-08 |
| Justin Willis | 8-2-0 | 2019-03-23 |
| Justin Wren | 13-2-0 | 2009-12-05 |
| Justine Kish | 7-4-0 | 2021-04-17 |
| Jutaro Nakao | 25-19-4 | 2002-03-22 |
| Kaan Ofli | 15-4-1 | 2026-06-27 |
| Kai Asakura | 23-6-0 | 2026-08-29 |