| Fighter | Record | Last Bout |
|---|---|---|
| Aleksei Kunchenko | 20-2-0 | 2020-03-14 |
| Alex Karalexis | 10-6-0 | 2006-01-16 |
| Aliaskhab Khizriev | 14-0-0 (1 NC) | 2024-02-03 |
| Anton Kuivanen | 24-10-0 | 2013-02-23 |
| Bharat Kandare | 5-3-0 | 2017-11-25 |
| Brad Katona | 16-5-0 | 2025-05-10 |
| Brad Kohler | 12-15-0 | 1999-09-24 |
| Brian Kelleher | 24-16-0 | 2024-07-20 |
| Bruno Korea | 7-3-0 | 2015-11-07 |
| CJ Keith | 8-4-0 | 2013-01-19 |
| Calvin Kattar | 23-10-0 | 2025-07-12 |
| Casey Kenney | 16-4-1 | 2021-08-07 |
| Cheick Kongo | 27-10-2 | 2013-04-27 |
| Chris Kelades | 9-3-0 | 2016-04-23 |
| Daniel Kelly | 13-4-0 | 2018-05-27 |
| David Kaplan | 3-4-0 | 2009-05-23 |
| Denis Kang | 35-16-2 (2 NC) | 2009-11-14 |
| Derrick Krantz | 22-12-0 | 2019-08-31 |
| Dong Hyun Kim | 22-4-1 (1 NC) | 2017-06-17 |
| Drakkar Klose | 16-3-1 | 2026-09-12 |
| Dustin Kimura | 11-3-0 | 2014-12-13 |
| Emily Kagan | 3-3-0 | 2015-12-10 |
| Erik Koch | 16-6-0 | 2019-07-27 |
| Ernesta Kareckaite | 6-2-1 | 2026-02-28 |
| Fatima Kline | 10-1-0 | 2026-07-18 |
| Geza Kalman | 4-9-0 | 1996-07-12 |
| Guram Kutateladze | 13-5-0 | 2025-03-22 |
| Impa Kasanganay | 9-2-0 | 2021-09-18 |
| Jacob Kilburn | 8-4-0 | 2021-01-16 |
| James Krause | 28-9-0 | 2020-10-17 |
| Jason Knight | 20-5-0 | 2018-11-03 |
| Jeremy Kennedy | 11-1-0 | 2018-02-10 |
| Jeremy Kimball | 15-8-0 | 2018-07-22 |
| Ji Yeon Kim | 9-7-2 | 2023-05-13 |
| Joe Kropschot | 9-3-0 | 2026-10-31 |
| John Kolosci | 15-9-0 | 2007-12-08 |
| Josefine Knutsson | 8-1-0 | 2024-12-14 |
| Josh Koscheck | 17-11-0 | 2015-03-21 |
| Julie Kedzie | 16-13-0 | 2013-12-06 |
| Justine Kish | 7-4-0 | 2021-04-17 |
| KB Bhullar | 8-2-0 | 2021-05-01 |
| Kaan Ofli | 15-4-1 | 2026-06-27 |
| Kai Asakura | 23-6-0 | 2026-08-29 |
| Kai Kamaka III | 18-8-1 | 2026-07-11 |
| Kai Kara-France | 25-12-0 (1 NC) | 2025-06-28 |
| Kailin Curran | 4-5-0 | 2017-11-25 |
| Kajan Johnson | 23-13-1 | 2018-09-15 |
| Kalib Starnes | 17-11-1 | 2008-04-19 |
| Kalindra Faria | 18-8-1 | 2018-08-25 |
| Kamal Shalorus | 9-5-2 | 2012-05-15 |