| Kai Kamaka III | Da Fighting Hawaiian | 2-3-1 | United States | Jul 11, 2026 |
| Sean King III | The King of New Orleans | 1-0-0 | United States | Sep 12, 2026 |
| Al Iaquinta | Raging | 9-6-0 | United States | Nov 6, 2021 |
| Khadis Ibragimov (inactive) | | 0-4-0 | Russia | Sep 26, 2020 |
| Minoki Ichihara (inactive) | | 0-1-0 | Japan | Mar 11, 1994 |
| Alibi Idiris | | 0-1-0 (1 NC) | Kazakhstan | Feb 21, 2026 |
| Dan Ige | 100K | 11-11-0 | United States | Sep 12, 2026 |
| Valeri Ignatov (inactive) | | 0-2-0 | Unknown | Sep 24, 1999 |
| Fabiano Iha (inactive) | | 3-4-0 | Brazil | Sep 28, 2001 |
| Zelim Imadaev (inactive) | | 0-3-0 | Unknown | Sep 5, 2020 |
| Nassourdine Imavov | The Sniper | 9-2-0 (1 NC) | Russia | Sep 6, 2025 |
| Brad Imes (inactive) | Hillbilly Heartthrob | 0-3-0 | United States | Apr 7, 2007 |
| Chris Indich (inactive) | | 0-2-0 | Unknown | Jun 28, 2014 |
| Guto Inocente (inactive) | | 0-2-0 | Unknown | Nov 7, 2014 |
| Enson Inoue (inactive) | Yamato Damashii | 1-0-0 | United States | May 30, 1997 |
| Naoki Inoue (inactive) | | 1-1-0 | Japan | Jun 23, 2018 |
| James Irvin (inactive) | The Sandman | 4-6-0 | United States | Aug 1, 2010 |
| Teruto Ishihara (inactive) | Yashabo | 3-5-1 | Japan | Feb 9, 2019 |
| Damir Ismagulov (inactive) | Qazaq | 5-2-0 | Russia | Jul 1, 2023 |
| Wallid Ismail (inactive) | | 0-1-0 | Brazil | Feb 7, 1997 |
| Leandro Issa (inactive) | Brodinho | 2-3-0 | Brazil | Sep 3, 2016 |
| Blagoy Ivanov (inactive) | Baga | 3-5-0 | Bulgaria | Jul 1, 2023 |
| Anthony Ivy (inactive) | Aquaman | 0-2-0 | United States | Sep 12, 2020 |
| Saygid Izagakhmaev | | 0-2-0 | Russia | Jul 25, 2026 |
| Yoislandy Izquierdo (inactive) | Cuba | 0-2-0 | Cuba | Jul 7, 2012 |