| Fighter | Record | Last Bout |
|---|---|---|
| Manoel Sousa | 15-1-0 | 2026-08-08 |
| Marcus Silveira | 6-4-0 (1 NC) | 1997-12-21 |
| Marina Spasic | 7-2-0 | 2026-08-01 |
| Mark Scanlon | 9-2-0 | 2010-11-13 |
| Mark Schultz | 1-1-0 | 1996-05-17 |
| Mark Striegl | 18-4-0 (1 NC) | 2022-02-19 |
| Martin Sano | 4-3-1 | 2021-09-25 |
| Martin Svensson | 15-6-0 | 2016-02-27 |
| Matt Sayles | 8-4-0 | 2021-12-18 |
| Matt Schnell | 17-11-0 (1 NC) | 2026-06-06 |
| Matt Serra | 11-7-0 | 2010-09-25 |
| Matthew Semelsberger | 11-8-0 | 2024-11-09 |
| Maurice Smith | 12-14-0 | 2000-11-17 |
| Mayra Bueno Silva | 10-7-1 (1 NC) | 2026-04-25 |
| Mike Santiago | 19-12-0 | 2018-06-09 |
| Mike Stumpf | 11-4-0 | 2013-01-26 |
| Mike Swick | 15-6-0 | 2015-07-11 |
| Muhammad Saidov | 10-0-0 | 2026-07-25 |
| Muslim Salikhov | 22-6-0 | 2026-09-12 |
| Natalia Silva | 20-5-1 | 2026-10-03 |
| Nate Schroeder | 11-10-0 | 2000-06-09 |
| Navajo Stirling | 11-0-0 | 2026-08-01 |
| Nazim Sadykhov | 11-3-1 | 2026-06-27 |
| Neil Seery | 16-13-0 | 2017-07-16 |
| Nick Sanzo | 1-1-0 | 1997-02-07 |
| Nick Serra | 7-3-0 | 2002-06-22 |
| Niklas Stolze | 12-6-0 | 2022-06-04 |
| Ollie Schmid | 4-3-0 | 2026-05-02 |
| Oumar Sy | 12-3-0 | 2026-09-05 |
| Ovince Saint Preux | 27-18-0 | 2024-10-05 |
| Pat Sabatini | 22-5-0 | 2026-05-09 |
| Pat Schilling | 5-2-0 | 2012-06-01 |
| Patrick Smith | 20-17-0 | 1995-07-14 |
| Paul Sass | 14-2-0 | 2013-02-16 |
| Paulo Santos | 0-3-0 | 1998-10-16 |
| Pete Sell | 10-7-0 | 2009-03-07 |
| Pete Spratt | 25-23-0 | 2007-06-12 |
| Peter Sobotta | 17-7-1 | 2020-07-25 |
| Punahele Soriano | 13-5-0 | 2026-09-05 |
| Quillan Salkilld | 13-1-0 | 2026-08-08 |
| Rameau Thierry Sokoudjou | 18-18-0 | 2008-10-18 |
| Rayanne dos Santos | 14-9-0 | 2025-05-31 |
| Renato Sobral | 37-11-0 | 2007-08-25 |
| Richie Smullen | 3-1-1 | 2018-07-06 |
| Rick Story | 19-9-0 | 2016-08-20 |
| Ricky Simon | 22-7-1 | 2026-09-26 |
| Robert Sanchez | 8-2-0 | 2018-09-08 |
| Roberto Soldic | 21-4-0 | 2026-10-03 |
| Rodrigo Sezinando | 9-2-0 | 2025-09-13 |
| Roldan Sangcha'an | 4-2-0 | 2015-05-16 |