| Fighter | Record | Last Bout |
|---|---|---|
| Krzysztof Jotko | 24-6-0 | 2022-10-01 |
| Krzysztof Soszynski | 26-12-1 | 2011-12-10 |
| Kuniyoshi Hironaka | 23-9-0 | 2008-04-19 |
| Kurt Pellegrino | 16-7-0 | 2011-03-19 |
| Kwan Ho Kwak | 9-2-0 | 2017-06-17 |
| Kyle Bochniak | 8-5-0 | 2019-10-18 |
| Kyle Bradley | 19-12-0 (1 NC) | 2010-01-11 |
| Kyle Kingsbury | 11-6-0 (1 NC) | 2014-07-26 |
| Kyle Noke | 22-10-1 | 2016-11-26 |
| Kyle Stewart | 11-3-0 | 2019-07-27 |
| Kyle Watson | 13-8-1 | 2011-04-30 |
| Kyung Ho Kang | 19-11-0 (1 NC) | 2024-06-22 |
| Leo Kuntz | 18-4-1 | 2015-11-28 |
| Mark Kerr | 15-11-0 (1 NC) | 1997-10-17 |
| Martin Kampmann | 20-7-0 | 2013-08-28 |
| Masanori Kanehara | 26-12-5 | 2016-01-02 |
| Michael Kuiper | 15-5-0 | 2013-10-26 |
| Mike King | 5-1-0 | 2014-07-19 |
| Mike Kyle | 22-14-1 (2 NC) | 2005-02-05 |
| Nadia Kassem | 5-2-0 | 2019-10-05 |
| Naoyuki Kotani | 34-14-7 | 2015-09-26 |
| Pannie Kianzad | 17-9-0 | 2024-08-10 |
| Pascal Krauss | 11-2-0 | 2013-08-31 |
| Paul Kelly | 14-5-0 | 2011-02-05 |
| Rob Kimmons | 25-9-0 | 2011-03-03 |
| Rustam Khabilov | 24-4-0 | 2019-11-09 |
| Saidyokub Kakhramonov | 10-3-0 | 2022-12-17 |
| Sanae Kikuta | 31-9-3 (1 NC) | 2000-04-14 |
| Sarah Kaufman | 18-4-0 (1 NC) | 2015-12-19 |
| Sergey Khandozhko | 28-6-1 | 2022-04-23 |
| Sirwan Kakai | 12-5-0 | 2015-08-08 |
| Steve Kennedy | 24-8-0 | 2015-11-14 |
| Syuri Kondo | 6-3-0 | 2019-06-22 |
| Tatsuya Kawajiri | 36-11-2 | 2016-08-06 |
| Tim Kennedy | 18-6-0 | 2016-12-10 |
| Tony Kelley | 8-3-0 | 2022-06-18 |
| Tsuyoshi Kohsaka | 27-19-2 | 2002-05-10 |
| William Knight | 11-5-0 | 2023-02-18 |
| Yuki Kondo | 60-33-9 | 2001-06-29 |
| Yusaku Kinoshita | 6-3-0 | 2023-08-26 |
| Yusuke Kasuya | 9-3-0 | 2016-11-26 |