text: William Manchester – author and historian
  Herman J. Mankiewicz – Oscar-winning screenwriter of Citizen Kane who also served in the United States Army Air Service
  Arman T. Manookian – artist of Hawaiian themes
  Mike Mansfield – U.S. Representative and Senator for Montana, Longest-serving Senate Majority Leader, U.S. Ambassador to Japan, co-author of the Douglas–Mansfield Bill (1951) supporting the U.S. Marine Corps.
  Karl Marlantes –  businessman, author of Matterhorn: A Novel of the Vietnam War
  Lee Marvin – Academy Award-winning actor (Cat Ballou)
  Robert F. Marx – pioneer scuba diver and author
  Carlo Mastrototaro – Mafia boss
  Al Matthews – actor and singer known for playing Gunny Apone in Aliens (1986) directed by James Cameron
  Tim Matheson – American Actor, star of Animal House and Fletch
  Bob Mathias – two-time Olympic champion in the decathlon, U.S. Congressman (California-R)
  James Mattis – United States Secretary of Defense
  Sam Mele – baseball player and manager
  Ronald Meyer – Vice Chairman of NBCUniversal, former president and Chief Operating Officer of Universal Studios
  Joseph McCarthy – U.S. Republican Senator from Wisconsin best known for "McCarthyism", in reference to his anti-communist practices which included blacklisting
  Hugh McColl – former chairman and CEO of Bank of America
  Pete McCloskey – U.S. Congressman (California-R)