| Dong Hyun Ma (inactive) | Maestro | 3-5-0 | South Korea | Dec 21, 2019 |
| Jason MacDonald (inactive) | The Athlete | 6-8-0 | Canada | May 15, 2012 |
| Rob MacDonald (inactive) | Maximus | 1-2-0 | Canada | Aug 26, 2006 |
| Rory MacDonald (inactive) | Red King | 9-4-0 | Canada | Jun 18, 2016 |
| Ryan MacDonald (inactive) | Main Event | 0-2-0 | United States | Sep 14, 2019 |
| William Macario (inactive) | Patolino | 1-3-0 | United States | Feb 22, 2015 |
| Caio Machado (inactive) | Bigfoot | 0-3-0 | Brazil | Nov 2, 2024 |
| Lyoto Machida (inactive) | The Dragon | 16-8-0 | Brazil | May 12, 2018 |
| War Machine (inactive) | | 1-1-0 | Unknown | May 24, 2008 |
| Anthony Macias (inactive) | Mad Dog | 1-2-0 | United States | Jul 14, 1995 |
| Reza Madadi (inactive) | Mad Dog | 3-4-0 | Unknown | May 28, 2017 |
| Jack Della Maddalena | | 8-2-0 | Australia | May 2, 2026 |
| Don Madge (inactive) | Magic Man | 2-0-0 | South Africa | Sep 7, 2019 |
| Ryan Madigan (inactive) | | 0-1-0 | United States | Mar 7, 2009 |
| Jon Madsen (inactive) | | 4-1-0 | United States | Mar 26, 2011 |
| Mark Madsen (inactive) | The Olympian | 4-2-0 | Denmark | Nov 11, 2023 |
| Leonardo Mafra (inactive) | Macarrao | 1-3-0 | Brazil | Jul 18, 2015 |
| Bernardo Magalhaes (inactive) | Trekko | 0-2-0 | Brazil | Jun 8, 2012 |
| Caio Magalhaes (inactive) | Hellboy | 4-3-0 | Brazil | Sep 10, 2016 |
| Vinny Magalhaes (inactive) | Pezao | 1-4-0 | Brazil | Aug 3, 2013 |
| Angela Magana (inactive) | Your Majesty | 0-3-0 | United States | Dec 2, 2017 |
| Neil Magny | The Haitian Sensation | 25-13-0 | United States | Aug 15, 2026 |
| Abus Magomedov | | 5-3-0 | Russia | Jun 27, 2026 |
| Murtazali Magomedov | The Highlight | 1-0-0 | Kyrgyzstan | Jun 20, 2026 |
| Rashid Magomedov (inactive) | Highlander | 5-1-0 | Russia | Apr 15, 2017 |
| Ruslan Magomedov (inactive) | Leopard | 3-0-0 | Russia | Oct 3, 2015 |
| Shara Magomedov | Bullet | 6-1-0 | Russia | Jun 27, 2026 |
| Zabit Magomedsharipov (inactive) | | 6-0-0 | Russia | Nov 9, 2019 |
| John Maguire (inactive) | The One | 2-3-0 | United Kingdom | Jun 15, 2013 |
| Maheshate | | 2-4-0 | Unknown | Aug 23, 2025 |
| Bill Mahood (inactive) | The Butcher | 0-1-0 | Canada | Jun 4, 2005 |
| Demian Maia (inactive) | | 22-11-0 | Brazil | Jun 12, 2021 |
| Jennifer Maia | | 6-6-0 | Brazil | Oct 14, 2023 |
| Levan Makashvili (inactive) | The Hornet | 1-1-1 | United States | Jan 30, 2016 |
| John Makdessi | The Bull | 11-9-0 | Canada | Sep 9, 2023 |
| Islam Makhachev | | 18-1-0 | Russia | Aug 15, 2026 |
| Zach Makovsky (inactive) | Fun Size | 3-4-0 | United States | Dec 10, 2016 |
| Azat Maksum (inactive) | Qazaq | 1-3-0 | Kazakhstan | Oct 25, 2025 |
| Fabio Maldonado (inactive) | Caipira de Aco | 5-6-0 | Brazil | Nov 7, 2015 |
| Bea Malecki (inactive) | | 2-1-0 | Sweden | Aug 21, 2021 |
| Nazareno Malegarie (inactive) | El Tigre | 0-1-0 | Argentina | Sep 5, 2015 |
| Jacob Malkoun | Mamba | 6-3-0 | Australia | May 2, 2026 |
| Mike Malott | Proper | 7-1-0 | United States | Apr 18, 2026 |
| Troy Mandaloniz (inactive) | Rude Boy | 1-1-0 | United States | Feb 21, 2009 |
| Nate Maness (inactive) | Mayhem | 5-2-0 | United States | Jun 15, 2024 |
| Jon Manley (inactive) | | 0-1-0 | United States | Feb 23, 2013 |
| Marnic Mann | The Sawed-Off Savage | 0-2-0 | United States | Apr 27, 2024 |
| Jimi Manuwa (inactive) | Poster Boy | 6-6-0 | United States | Jun 1, 2019 |
| Cristiano Marcello (inactive) | | 1-3-0 | Brazil | Feb 15, 2014 |
| Daniel Marcos (inactive) | Soncora | 5-1-0 (1 NC) | Peru | Nov 8, 2025 |
| Jose Maria (inactive) | No Chance | 0-2-0 | Brazil | Nov 9, 2013 |
| Marcos Mariano (inactive) | Dhalsim | 0-2-0 | Unknown | Sep 21, 2019 |
| Enrique Marin (inactive) | Wasabi | 0-2-0 | United States | Jul 9, 2016 |
| Chepe Mariscal | Machine Gun | 5-1-0 | United States | Nov 15, 2025 |
| Ronny Markes (inactive) | | 3-2-0 | Brazil | Mar 23, 2014 |
| Rory Markham (inactive) | | 1-2-0 | United States | Mar 27, 2010 |
| Randa Markos (inactive) | Quiet Storm | 7-10-1 | Iraq | Oct 23, 2021 |
| Christina Marks (inactive) | | 0-1-0 | United States | Dec 1, 2017 |
| Brendon Marotte (inactive) | The Kid | 0-2-0 | United States | Sep 7, 2024 |
| Nate Marquardt (inactive) | The Great | 13-12-0 | United States | Nov 11, 2017 |
| Danilo Marques (inactive) | | 2-2-0 | Brazil | Feb 5, 2022 |
| Wendell Oliveira Marques (inactive) | The Machine | 0-2-0 | Unknown | May 30, 2015 |
| Julian Marquez (inactive) | The Cuban Missile Crisis | 3-5-0 | United States | Mar 1, 2025 |
| Carmelo Marrero (inactive) | The Fury | 1-3-0 | United States | Apr 1, 2009 |
| Cesar Marscucci (inactive) | | 1-0-0 | Unknown | Oct 16, 1998 |
| John Marsh (inactive) | | 0-1-0 | United States | Apr 16, 2005 |
| Eliot Marshall (inactive) | Fire | 3-3-0 | United States | Oct 29, 2011 |
| Francis Marshall | Fire | 4-3-0 | United States | Apr 25, 2026 |
| Jack Marshman (inactive) | The Hammer | 3-5-0 | United Kingdom | Oct 31, 2020 |
| Anthony Rocco Martin (inactive) | | 9-6-0 | United States | Jun 6, 2020 |
| Eric Martin (inactive) | | 0-1-0 | Unknown | Feb 7, 1997 |
| Justin Martin (inactive) | | 1-0-0 | United States | Feb 7, 1997 |
| Mallory Martin (inactive) | | 1-3-0 | United States | Dec 4, 2021 |
| Terry Martin (inactive) | | 2-4-0 | United States | Feb 2, 2008 |
| Adrian Luna Martinetti | | 0-1-0 | Unknown | Apr 25, 2026 |
| Danny Martinez (inactive) | The Gremlin | 1-3-0 | United States | Nov 14, 2015 |
| David Martinez | | 4-0-0 | Mexico | Sep 12, 2026 |
| Henry Martinez (inactive) | Sicario | 1-2-0 | United States | Dec 8, 2012 |
| Jonathan Martinez | Dragon | 10-5-0 | United States | Nov 16, 2024 |
| Mana Martinez (inactive) | ManaBoi | 2-2-0 | United States | Mar 4, 2023 |
| Melissa Martinez (inactive) | Super Mely | 1-2-0 | Mexico | Jul 12, 2025 |
| Rainy Martinez (inactive) | | 0-1-0 | Unknown | Feb 7, 1997 |
| Roque Martinez (inactive) | | 0-3-0 | United States | Jun 19, 2021 |
| Victor Martinez (inactive) | The Brick | 0-2-0 | United States | May 18, 2024 |
| Adriano Martins (inactive) | | 4-3-0 | Brazil | Sep 9, 2017 |
| Lucas Martins (inactive) | Mineiro | 4-3-0 | Brazil | Apr 10, 2016 |
| Bristol Marunde (inactive) | | 0-2-0 | United States | Aug 3, 2013 |
| Mike Massenzio (inactive) | The Master of Disaster | 2-5-0 | United States | May 5, 2012 |
| Jorge Masvidal (inactive) | Gamebred | 12-10-0 | United States | Apr 8, 2023 |
| Tateki Matsuda (inactive) | Tech | 0-2-0 | United States | Jan 18, 2015 |
| Jean Matsumoto | | 4-2-0 | Brazil | Jun 27, 2026 |
| Connor Matthews (inactive) | The Controller | 0-3-0 | United States | May 17, 2025 |
| Jake Matthews | The Celtic Kid | 16-8-0 | Australia | May 30, 2026 |
| John Matua (inactive) | | 0-1-0 | United States | Jul 14, 1995 |
| Francesco Maturi (inactive) | | 0-1-0 | Unknown | Sep 8, 1995 |
| Vladimir Matyushenko (inactive) | The Janitor | 7-5-0 | Russia | Jan 26, 2013 |
| Miranda Maverick | Fear The | 8-4-0 | United States | Jun 14, 2025 |
| Nick Maximov (inactive) | | 2-2-0 | United States | Oct 15, 2022 |
| Jack May (inactive) | The Outlaw | 0-2-0 | Unknown | Aug 16, 2014 |
| Don'Tale Mayes (inactive) | Lord Kong | 4-7-0 (1 NC) | United States | May 3, 2025 |
| Gray Maynard (inactive) | | 11-7-1 (1 NC) | United States | Oct 6, 2018 |
| Gina Mazany (inactive) | Danger | 2-6-0 | United States | Apr 30, 2022 |
| Sabina Mazo (inactive) | Colombian Queen | 3-4-0 | Colombia | Mar 12, 2022 |
| Michael McBride (inactive) | | 0-2-0 | United States | Apr 22, 2017 |
| Ian McCall (inactive) | Uncle Creepy | 2-3-1 | United States | Jan 31, 2015 |
| Molly McCann (inactive) | Meatball | 7-7-0 | United Kingdom | Mar 22, 2025 |
| Charles McCarthy (inactive) | Chainsaw | 1-2-0 | United States | Apr 19, 2008 |
| Eric McConico | | 2-3-0 | United States | Aug 15, 2026 |
| Sean McCorkle (inactive) | | 1-2-0 | United States | Mar 26, 2011 |
| Kris McCray (inactive) | Savage | 0-3-0 | United States | Mar 26, 2011 |
| Tamdan McCrory (inactive) | The Barncat | 4-5-0 | United States | Oct 1, 2016 |
| Justin McCully (inactive) | The Insane One | 2-2-0 | United States | Aug 29, 2009 |
| Robert McDaniel (inactive) | Bubba | 1-2-0 | Unknown | Mar 15, 2014 |
| Michael McDonald (inactive) | Mayday | 6-3-0 | United States | Jul 13, 2016 |
| Drew McFedries (inactive) | The Massacre | 4-5-0 | United States | Sep 19, 2009 |
| Court McGee | The Crusher | 11-14-0 | United States | Oct 3, 2026 |
| Gan McGee (inactive) | The Giant | 2-2-0 | United States | Sep 26, 2003 |
| Marcus McGhee | The Maniac | 6-1-0 | United States | Oct 3, 2026 |
| Ryan McGillivray (inactive) | The Kid | 0-1-0 | Unknown | Jun 4, 2011 |
| Jack McGlaughlin (inactive) | | 0-1-0 | Unknown | Jul 14, 1995 |
| Conor McGregor | The Notorious | 10-5-0 | Ireland | Jul 11, 2026 |
| Antonio McKee (inactive) | Mandingo | 0-1-0 | United States | Jan 1, 2011 |
| Rhys McKee (inactive) | Skeletor | 1-5-0 | Ireland | Sep 6, 2025 |
| Cory McKenna (inactive) | Poppins | 3-3-0 | United Kingdom | Oct 12, 2024 |
| Cody McKenzie (inactive) | | 3-4-0 | United States | Dec 14, 2013 |
| Tim McKenzie (inactive) | | 0-1-0 | United States | Apr 1, 2009 |
| Terrance McKinney | T. Wrecks | 8-6-0 | United States | Jul 11, 2026 |
| Garreth McLellan (inactive) | Soldier Boy | 1-4-0 | South Africa | Mar 11, 2017 |
| Sara McMann (inactive) | | 7-6-0 | United States | Mar 26, 2022 |
| Tommy McMillen | Gun | 3-0-0 | United States | Sep 12, 2026 |
| James McSweeney (inactive) | The Hammer | 1-2-0 | United Kingdom | Oct 16, 2010 |
| Jackson McVey | The Moose | 2-2-0 | United States | Aug 22, 2026 |
| Tim Means | The Dirty Bird | 15-14-0 (1 NC) | United States | Oct 5, 2024 |
| Anistavio Medeiros (inactive) | Gasparzinho | 0-1-0 | Unknown | Jun 23, 2012 |
| Yancy Medeiros (inactive) | | 6-8-0 (1 NC) | United States | Jun 26, 2021 |
| MarQuel Mederos | | 4-0-1 | United States | Aug 22, 2026 |
| Uros Medic | The Doctor | 8-3-0 | Serbia | Aug 1, 2026 |
| Jose Daniel Medina (inactive) | Chicho | 0-4-0 | Bolivia | Feb 28, 2026 |
| Todd Medina (inactive) | El Tiburon | 1-1-0 | Unknown | Apr 7, 1995 |
| Emil Meek (inactive) | Valhalla | 1-3-0 | Norway | Feb 22, 2020 |
| Gerald Meerschaert | GM3 | 12-14-0 | United States | May 2, 2026 |
| Jordan Mein (inactive) | Young Gun | 5-4-0 | Unknown | Jul 28, 2018 |
| Brian Melancon (inactive) | | 1-1-0 | United States | Aug 28, 2013 |
| Brandon Melendez (inactive) | The Murderer | 0-1-0 | Unknown | Jun 23, 2007 |
| Gilbert Melendez (inactive) | El Nino | 1-6-0 | United States | Jul 6, 2019 |
| Anna Melisano | Bandana | 0-1-0 | United States | Jul 18, 2026 |
| Marcelo Mello (inactive) | | 1-0-0 | Unknown | May 7, 1999 |
| Vanessa Melo (inactive) | | 1-3-0 | Brazil | Jan 16, 2021 |
| Antonio Mendes (inactive) | Samurai | 0-2-0 | United States | Jan 17, 2009 |
| Augusto Mendes (inactive) | Tanquinho | 1-2-0 | Brazil | Apr 15, 2017 |
| Chad Mendes (inactive) | Money | 9-5-0 | United States | Dec 29, 2018 |
| Eddie Mendez (inactive) | | 0-1-0 | United States | Jun 8, 2013 |
| Mateus Mendonca | Bocao | 0-3-0 | Brazil | Feb 24, 2024 |
| Alvaro Herrera Mendoza (inactive) | Chango | 1-3-0 | Unknown | Jul 28, 2018 |
| Ding Meng | | 0-2-0 | China | Aug 29, 2026 |
| Alonzo Menifield | Atomic | 12-6-1 | United States | Sep 19, 2026 |
| Ivan Menjivar (inactive) | The Pride of El Salvador | 4-5-0 | United States | Mar 1, 2014 |
| Dave Menne (inactive) | The Warrior | 2-4-0 | Unknown | Dec 13, 2006 |
| Joe Merritt (inactive) | | 0-1-0 | Unknown | Jun 27, 2015 |
| Bia Mesquita | The Lady GOAT | 3-0-0 | Brazil | Jun 20, 2026 |
| Jonathan Meunier (inactive) | District | 1-1-0 | Canada | Nov 26, 2016 |
| Yaotzin Meza (inactive) | | 2-4-0 (1 NC) | United States | Feb 27, 2016 |
| Guy Mezger (inactive) | | 4-1-0 | United States | Mar 5, 1999 |
| Jonathan Micallef | The Captain | 3-0-0 | Australia | May 2, 2026 |
| Andreas Michailidis (inactive) | The Spartan | 1-3-0 | Greece | Jun 4, 2022 |
| David Michaud (inactive) | BullDawg | 1-2-0 | United States | Apr 25, 2015 |
| Kristof Midoux (inactive) | The Hurricane | 0-1-0 | Unknown | Aug 17, 2006 |
| Keith Mielke (inactive) | | 0-1-0 | United States | Feb 16, 1996 |
| Bojan Mihajlovic (inactive) | | 0-3-0 | Serbia | Sep 2, 2017 |
| Billy Miles (inactive) | The Kid | 0-1-0 | Unknown | Dec 8, 2007 |
| Pat Miletich (inactive) | The Croatian Sensation | 8-2-0 | United States | Mar 22, 2002 |
| Curtis Millender (inactive) | Curtious | 3-2-0 | United States | Apr 13, 2019 |
| Cole Miller (inactive) | Magrinho | 10-9-0 (1 NC) | United States | Dec 17, 2016 |
| Dan Miller (inactive) | | 6-7-0 | United States | Jul 12, 2015 |
| Jason Miller (inactive) | Mayhem | 0-3-0 | United States | May 26, 2012 |
| Jim Miller | A-10 | 28-18-0 (1 NC) | United States | May 9, 2026 |
| Juliana Miller | Killer | 3-3-0 | United States | Aug 8, 2026 |
| Phillip Miller (inactive) | | 2-0-0 | United States | Nov 22, 2002 |
| Ty Miller | Thriller | 2-0-0 | United States | Aug 8, 2026 |
| Che Mills (inactive) | Beautiful | 2-1-0 (1 NC) | United Kingdom | Feb 16, 2013 |
| Nina Milosevic | Queen Beast | 1-0-0 | Unknown | Aug 1, 2026 |
| Adam Milstead (inactive) | The Prototype | 1-2-0 (1 NC) | United States | Dec 15, 2018 |
| Alberto Mina (inactive) | Soldier of God | 3-1-0 | Brazil | May 12, 2018 |
| Artur Minev | Headhunter | 0-1-0 | Ukraine | May 16, 2026 |
| Shi Ming (inactive) | | 1-0-0 | Unknown | Nov 23, 2024 |
| Zhang Mingyang | Mountain Tiger | 3-2-0 | China | May 30, 2026 |
| Darrick Minner (inactive) | | 2-4-0 | United States | Nov 5, 2022 |
| Ikuhisa Minowa (inactive) | Minowaman | 1-0-0 | United States | Apr 14, 2000 |
| Carlton Minus (inactive) | Clutch | 0-2-0 | United States | Dec 19, 2020 |
| Stipe Miocic (inactive) | | 14-5-0 | United States | Nov 16, 2024 |
| Frank Mir (inactive) | | 16-11-0 | United States | Mar 19, 2016 |
| Gabriel Miranda (inactive) | Fly | 1-3-0 | Brazil | Mar 29, 2025 |
| Mario Miranda (inactive) | | 1-3-0 | Brazil | Mar 26, 2011 |
| Richie Miranda | El Machete | 0-1-0 | United States | Aug 8, 2026 |
| Vitor Miranda (inactive) | Lex Luthor | 3-4-0 | Brazil | Jul 22, 2018 |
| Dokonjonosuke Mishima (inactive) | | 0-2-0 | Japan | Apr 5, 2007 |
| Bryce Mitchell | Thug Nasty | 10-3-0 | United States | Jun 6, 2026 |
| Danny Mitchell (inactive) | The Cheesecake Assassin | 0-2-0 | United Kingdom | Aug 23, 2014 |
| David Mitchell (inactive) | Daudi | 1-4-0 | Unknown | Oct 9, 2013 |
| Felix Lee Mitchell (inactive) | | 0-3-0 | Unknown | Dec 7, 1996 |
| Terrence Mitchell | | 0-2-0 | United States | Sep 16, 2023 |
| Roman Mitichyan (inactive) | | 1-1-0 | Armenia | Apr 2, 2008 |
| Matt Mitrione (inactive) | | 9-5-0 | United States | Jan 17, 2016 |
| Eiji Mitsuoka (inactive) | | 0-2-0 | Japan | Aug 11, 2012 |
| Patchy Mix (inactive) | No Love | 0-2-0 | United States | Oct 4, 2025 |
| Takeya Mizugaki (inactive) | | 8-6-0 | Japan | Dec 17, 2016 |
| Mizuki | | 3-1-0 | Unknown | Oct 25, 2025 |
| Roxanne Modafferi (inactive) | The Happy Warrior | 4-8-0 | United States | Feb 12, 2022 |
| Bobby Moffett (inactive) | The Wolfman | 0-2-0 (1 NC) | United States | Aug 10, 2019 |
| Nate Mohr (inactive) | | 1-3-0 | United States | Jan 17, 2009 |
| Renato Moicano | | 13-7-0 | Brazil | Apr 4, 2026 |
| Thiago Moises (inactive) | | 8-8-0 | Brazil | Apr 18, 2026 |
| Muhammad Mokaev (inactive) | The Punisher | 7-0-0 | Unknown | Jul 27, 2024 |
| Ashkan Mokhtarian (inactive) | The Assassin | 0-2-0 | Iran | Nov 18, 2017 |
| Suman Mokhtarian (inactive) | | 0-2-0 | Australia | Dec 21, 2019 |
| Jeff Molina (inactive) | El Jefe | 3-0-0 | United States | Jun 4, 2022 |
| Rudyard Moncayo (inactive) | | 0-1-0 | Unknown | Jul 14, 1995 |
| Jeff Monson (inactive) | The Snowman | 4-3-0 | United States | Nov 18, 2006 |
| Darrell Montague (inactive) | Mongoose | 0-3-0 | United States | Jul 12, 2015 |
| Michelle Montague | The Wild One | 2-0-0 | New Zealand | Apr 25, 2026 |
| Jose Montanha | | 1-0-0 | Unknown | Aug 8, 2026 |
| Augusto Montano (inactive) | Dodger | 1-2-0 | Mexico | Sep 17, 2016 |
| Erick Montano (inactive) | Perry | 1-2-0 | Mexico | Nov 5, 2016 |
| Nicco Montano (inactive) | | 1-1-0 | United States | Jul 13, 2019 |
| Sofia Montenegro | La Bruja | 0-1-0 | Argentina | Sep 5, 2026 |
| Alberto Montes | The Promise | 1-1-0 | Venezuela | Jul 18, 2026 |
| Steve Montgomery (inactive) | The Creepy Weasel | 0-2-0 | United States | Nov 14, 2015 |
| James Moontasri (inactive) | Moon Walker | 2-4-0 | Germany | Dec 17, 2016 |
| Homer Moore (inactive) | The Rock | 0-1-0 | United States | Nov 2, 2001 |
| Marlon Moraes (inactive) | Magic | 5-6-0 | Brazil | Mar 12, 2022 |
| Sergio Moraes (inactive) | The Panther | 8-5-1 | Brazil | Nov 16, 2019 |
| Sheymon Moraes (inactive) | | 2-3-0 | Brazil | Jul 13, 2019 |
| John Moraga (inactive) | | 8-6-0 | United States | Aug 25, 2018 |
| Albert Morales (inactive) | The Warrior | 1-4-1 | United States | Feb 24, 2018 |
| Joseph Morales | Bopo | 3-3-0 | United States | Sep 12, 2026 |
| Leonardo Morales (inactive) | Chimy | 0-2-0 | Nicaragua | Jun 6, 2015 |
| Michael Morales | | 7-0-0 | Ecuador | Nov 15, 2025 |
| Omar Morales (inactive) | Venezuelan Fighter | 3-4-0 | Venezuela | Mar 18, 2023 |
| Vince Morales (inactive) | Vandetta | 3-9-0 | United States | May 2, 2026 |
| Sarah Moras (inactive) | Cheesecake | 3-6-0 | Canada | Jan 16, 2021 |
| Christian Morecraft (inactive) | | 1-3-0 | United States | Jan 20, 2012 |
| Glaico Franca Moreira (inactive) | Nego | 1-2-0 | Unknown | Sep 24, 2016 |
| Joe Moreira (inactive) | | 1-1-0 | Unknown | Jul 27, 1997 |
| Richardson Moreira (inactive) | Rick Monstro | 0-2-0 | Brazil | Jan 31, 2015 |
| Vinicius Moreira (inactive) | Mamute | 0-4-0 | Unknown | Jan 20, 2021 |
| Brandon Moreno | The Assassin Baby | 12-7-2 | Mexico | Sep 12, 2026 |
| Dan Moret (inactive) | The Hitman | 0-3-0 | United States | Jun 29, 2019 |
| Peggy Morgan (inactive) | The Daywalker | 0-1-0 | United States | Nov 30, 2013 |
| Sammy Morgan (inactive) | The Squeeze | 0-2-0 | United States | Aug 17, 2006 |
| Alex Morono (inactive) | The Great White | 13-10-0 (1 NC) | United States | Feb 7, 2026 |
| Maryna Moroz (inactive) | Iron Lady | 6-6-0 | Ukraine | Mar 9, 2024 |
| Sergey Morozov | | 3-2-0 | Kazakhstan | Dec 17, 2022 |
| Brad Morris (inactive) | | 0-2-0 | Australia | Sep 17, 2008 |
| Scott Morris (inactive) | | 1-1-0 | United States | Mar 11, 1994 |
| Humberto Brown Morrison (inactive) | | 0-1-0 | Unknown | Nov 15, 2014 |
| Harry Moskowitz (inactive) | Dirty | 0-2-0 | United States | May 15, 1998 |
| Carlos Mota (inactive) | Tizil | 0-1-0 | Brazil | Oct 29, 2022 |
| Nikolas Motta | Iron | 3-3-0 (1 NC) | Brazil | Jun 21, 2025 |
| Eduarda Moura | Ronda | 3-3-0 | Brazil | Sep 19, 2026 |
| Flavio Luiz Moura (inactive) | | 0-1-0 | Unknown | Jul 16, 1999 |
| Gegard Mousasi (inactive) | | 9-3-0 | Iran | Apr 8, 2017 |
| Kris Moutinho (inactive) | | 0-4-0 | United States | Feb 28, 2026 |
| Jamie Moyle (inactive) | | 1-2-0 | United States | Jul 7, 2018 |
| Askar Mozharov (inactive) | | 0-1-0 | Ukraine | Jun 4, 2022 |
| Lauren Mueller (inactive) | Princess Tiger | 1-3-0 | United States | Oct 12, 2019 |
| Belal Muhammad | Remember the Name | 15-6-0 (1 NC) | United States | Jun 6, 2026 |
| Quinn Mulhern (inactive) | | 0-2-0 | United States | Jan 4, 2014 |
| James Mulheron (inactive) | | 0-1-0 | United Kingdom | Jul 16, 2017 |
| Jamie Mullarkey (inactive) | | 6-7-0 | Australia | Jan 31, 2026 |
| Jim Mullen (inactive) | | 0-1-0 | Unknown | Feb 7, 1997 |
| Melissa Mullins | No Mess | 2-3-0 | United Kingdom | Jun 20, 2026 |
| Pedro Munhoz (inactive) | The Young Punisher | 10-10-0 (2 NC) | Brazil | Nov 2, 2024 |
| Andre Muniz (inactive) | Sergipano | 6-4-0 | Brazil | Oct 4, 2025 |
| Alexander Munoz (inactive) | | 1-2-0 | United States | Jul 15, 2023 |
| Johnny Munoz | Kid Kvenbo | 2-4-0 | United States | Oct 7, 2023 |
| Mark Munoz (inactive) | The Filipino Wrecking Machine | 9-6-0 | United States | May 16, 2015 |
| Makhmud Muradov (inactive) | | 4-2-0 (1 NC) | Tajikistan | Feb 3, 2024 |
| Kanako Murata | | 1-2-0 | Japan | Oct 7, 2023 |
| Lauren Murphy | Lucky | 8-7-0 | United States | Jul 12, 2025 |
| Lerone Murphy | The Miracle | 9-1-1 | United Kingdom | Mar 21, 2026 |
| Tom Murphy (inactive) | | 1-0-0 | United States | Mar 4, 2006 |
| Lee Murray (inactive) | Lightning | 1-0-0 | United Kingdom | Jan 31, 2004 |
| Khalid Murtazaliev (inactive) | | 1-0-0 | Russia | Sep 15, 2018 |
| Azamat Murzakanov | The Professional | 6-1-0 | Russia | Apr 11, 2026 |
| Josias Musasa | The KO Wizard | 0-2-0 | Congo - Kinshasa | Sep 27, 2025 |
| Tofiq Musayev | | 2-1-0 | Azerbaijan | Aug 1, 2026 |
| Nicholas Musoke (inactive) | Nico | 3-3-0 | Sweden | May 28, 2017 |
| Magomed Mustafaev (inactive) | The Sniper | 3-2-0 | Russia | Feb 22, 2020 |
| Elvis Mutapcic (inactive) | The King | 0-2-1 | Unknown | Dec 3, 2016 |