| Little Rock Rangers | — | Little Rock | 2015 | — |
| Long Island Academy | National Premier Soccer League | — | 2006 | — |
| Long Island Rough Riders | A-League, USL Second Division, USL League Two | Long Island | 1994 | Hofstra University Soccer Stadium |
| Long Island Rough Riders women | United Women's Soccer | Uniondale | 1994 | Hofstra University Soccer Stadium |
| Los Angeles Aztecs | North American Soccer League | Los Angeles | 11 December 1973 | Weingart Stadium |
| Los Angeles FC | Major League Soccer | Los Angeles | 2014 | BMO Stadium |
| Los Angeles Force | National Independent Soccer Association | Los Angeles | 2019 | — |
| Los Angeles Heat | — | Los Angeles | 1986 | — |
| Los Angeles Heroes | USL League Two | — | 1993 | — |
| Los Angeles Kickers | — | Los Angeles | 1951 | — |
| Los Angeles Lazers | Major Indoor Soccer League | — | 1982 | Kia Forum |
| Los Angeles Legends | USL W-League | — | 2008 | — |
| Los Angeles Rampage | Women's Premier Soccer League | — | 2007 | John Elway Stadium |
| Los Angeles Salsa | American Professional Soccer League | — | 1993 | Titan Stadium |
| Los Angeles Skyhawks | — | Los Angeles | 1976 | — |
| Los Angeles Sol | Women's Professional Soccer | Carson | 2007 | Dignity Health Sports Park |
| Los Angeles Strikers | USL W-League | — | 2011 | — |
| Los Angeles Toros | National Professional Soccer League | Los Angeles | 1967 | Los Angeles Memorial Coliseum |
| Loudoun United FC | USL Championship | Leesburg | 18 July 2018 | Audi Field |
| Louisville City FC | USL Championship | Louisville | 4 June 2014 | Lynn Family Stadium |
| Louisville Lightning | Major Arena Soccer League | — | 2009 | — |
| Lynch's Irish Pub F.C. | — | — | 1999 | — |
| MagicJack | Women's Professional Soccer | Boca Raton | 2001 | — |
| Maine Sting | National Premier Soccer League | — | 2008 | — |
| Maine USL W League team | USL W League | Portland | — | — |
| Manhattan Celtic FC | Eastern Premier Soccer League | New York City | — | — |
| Manhattan SC | — | Riverdale | — | Gaelic Park |
| Maryland Bobcats FC | National Independent Soccer Association | New York City | 2010 | Maryland SoccerPlex |
| Maryland Mania | A-League | — | 1999 | — |
| Mass United FC | National Premier Soccer League | — | 2009 | — |
| Massachusetts Twisters | — | — | 2003 | The Big E Coliseum |
| Maunabo Leones | Liga Nacional de Fútbol de Puerto Rico | Maunabo | 1960 | — |
| Mayagüez FC | Puerto Rico Soccer League | — | 2004 | Mayagüez Athletics Stadium |
| Memphis 901 FC | USL Championship | Memphis | 8 January 2018 | AutoZone Park |
| Memphis Americans | Major Indoor Soccer League | — | 1981 | — |
| Memphis Express | USL League Two | — | 2002 | — |
| Memphis Rogues | North American Soccer League | Memphis | 1978 | — |
| Miami Americans | — | Miami | 1979 | — |
| Miami FC | USL Championship | Miami | 2015 | Pitbull Stadium |
| Miami Fusion | Major League Soccer | Fort Lauderdale | 1997 | Lockhart Stadium |
| Miami Fusion FC | National Premier Soccer League | — | 2014 | — |
| Miami Toros | North American Soccer League | Washington, D.C. | 1972 | Miami Orange Bowl |
| Michigan Stars FC | National Independent Soccer Association | Detroit | 1982 | Wisner Stadium |
| Milwaukee Rampage | A-League | Milwaukee | 1993 | Uihlein Soccer Park |
| Milwaukee Torrent | National Premier Soccer League | Milwaukee | January 2015 | — |
| Milwaukee Wave | Major Indoor Soccer League | — | 1984 | UW–Milwaukee Panther Arena |
| Minneapolis City SC | National Premier Soccer League | Minneapolis | 2015 | — |
| Minnesota Kicks | North American Soccer League | Minneapolis | 1976 | Metropolitan Stadium |