| MGM Holdings | business | Beverly Hills | February 11, 2005 |
| Miami University | public educational institution of the United States, public research university | Oxford | 1809 |
| Micro Instrumentation and Telemetry Systems | business | Albuquerque | 1970 |
| Microchip Technology | technology company, business, enterprise, public company | Chandler | 1989 |
| Microsoft Store | retail chain, subsidiary company | Redmond | October 22, 2009 |
| Middle-earth Enterprises | business | Berkeley | 2022 |
| Middlebury College | private not-for-profit educational institution, private university | — | 1800 |
| Midway Games | video game developer, business, enterprise, public company | Chicago | 1988 |
| Miller Brewing Company | brewery | Milwaukee | 1855 |
| Mills College at Northeastern University | private not-for-profit educational institution, women's college | — | 1852 |
| Milton Bradley Company | board game publishing company, business | East Longmeadow | 1860 |
| Minnesota State University, Mankato | public educational institution of the United States, public university | — | 1868 |
| Mises Institute | think tank, nonprofit organization, publishing house, educational institution | Auburn | 1982 |
| Mississippi State University | research university, unincorporated community, public educational institution of the United States, open-access publisher, land-grant university, public university | — | 1878 |
| MIT Media Lab | faculty, university research group | Cambridge | 1985 |
| Mobile County Public School System | school district in the United States | — | 1836 |
| Modern Language Association | nonprofit organization, open-access publisher, literary society, professional association, learned society | New York City | 1883 |
| Moderna | biopharmaceutical company, business, public company | Cambridge | 2010 |
| Mondelez International | food manufacturer, business, chocolaterie, public company | Chicago | 2012 |
| Monolith Productions | publishing house, video game developer | Kirkland | October 25, 1994 |
| Monsanto | multinational corporation, public company | St. Louis, Creve Coeur | 1901 |
| Monster Games | video game developer | Northfield | 1996 |
| Monster Inc. | business, enterprise | Brisbane | 1978 |
| Montclair State University | research university, public educational institution of the United States, public university | Montclair | 1908 |
| Moon Express | privately held company | Mountain View | 2010 |
| Mooney International Corporation | aerospace manufacturer | Kerrville | 1929 |
| Morehouse College | historically black college or university, college, private not-for-profit educational institution, school | Atlanta | 1867 |
| Morgan Creek Entertainment | film studio | Santa Monica | 1988 |
| Morgan Stanley | global systemically important bank, bank, business, enterprise, credit institution, public company | New York City | 1931 |
| Morgan State University | historically black college or university, public educational institution of the United States, university | Baltimore | 1867 |
| Morningstar, Inc. | financial services company, business, database, public company | Chicago | 1984 |
| MOS Technology | business, enterprise | Norristown | 1969 |
| Motion Picture Patents Company | film production company | United States | 1908 |
| Motorola Solutions | organization, business, enterprise, public company | Chicago | January 4, 2011 |
| MPEG LA | enterprise | Denver | 1996 |
| MSCI | business, public company | New York City | 1969 |
| MTV Entertainment Studios | film production company | Hollywood | 1991 |
| MTV Films | film production company | Los Angeles | 1996 |
| MUFG Union Bank | bank, business, financial institution | San Francisco | 1864 |
| Museum of Fine Arts, Houston | production company, nonprofit organization, art museum, museum | Houston | 1900 |
| MyFreeCams | adult camming website | — | March 19, 2002 |
| Mythic Entertainment | video game developer | Fairfax | 1995 |
| México. | business | Rome, San Clemente | 1999 |
| Naropa University | private not-for-profit educational institution, university | — | 1974 |
| Narus | business, software | Sunnyvale | 1997 |
| National Academy of Engineering | academy of sciences | Washington, D.C. | 1964 |
| National Airlines | airline | Orlando | 1985 |
| National Airlines | airline | Miami-Dade County | 1934 |