M
- Mike MacDougal
- Ken Macha
- Robert Machado
- José Macías
- Pete Mackanin
- Rob Mackowiak
- Mike Maddux
- Mickey Mahler
- Rick Mahler
- Gary Majewski
- Carlos Maldonado
- Bob Malloy
- Pepe Mangual
- Charlie Manning
- Julio Manón
- Fred Manrique
- Barry Manuel
- Jerry Manuel
- Leo Marentette
- Jason Marquis
- Chris Marrero
- Oreste Marrero
- Mike Marshall
- J. D. Martin
- Dave Martínez
- Dennis Martínez
- Manny Martínez
- Pedro Martínez
- Sandy Martínez
- Shairon Martis
- Clyde Mashore
- Jim Mason
- Henry Mateo
- Luis Matos
- Troy Mattes
- Ryan Mattheus
- Justin Maxwell
- Derrick May
- Rudy May
- Yunesky Maya
- Matt Maysey
- Ernie McAnally
- Tim McCarver
- Bob McClure
- Dave McDonald
- Will McEnaney
- Andy McGaffigan
- Dan McGinn *
- Ryan McGuire
- Tim McIntosh
- Dave McNally
- Sam Mejías
- Kevin Mench
- Orlando Mercado
- Orlando Merced
- José Mercedes
- Hensley Meulens
- Lastings Milledge
- Randy Miller
- Randy Milligan
- Brad Mills
- John Milner
- Tommy Milone
- Ryan Minor
- Garrett Mock
- Dale Mohorcic
- John Montague
- Willie Montañez
- Charlie Montoyo
- Luke Montz
- Balor Moore
- Bill Moore
- Trey Moore
- Tyler Moore
- David Moraga
- José Morales
- Mike Mordecai
- Nyjer Morgan
- Mike Morse
- Carl Morton *
- Guillermo Mota
- Manny Mota *
- James Mouton
- Arnie Muñoz
- Bobby Muñoz
- Dale Murray
Read more about this topic: Washington Nationals All-time Roster