| L.A. Wolves FC | United Premier Soccer League | — | 2014 | — |
| LA Galaxy | Major League Soccer | Los Angeles | 1995 | Dignity Health Sports Park |
| La Máquina FC | United Premier Soccer League | Santa Ana | 2011 | — |
| Lafayette Swamp Cats | USL League Two | — | 2000 | — |
| Lafayette SwampCats | Eastern Indoor Soccer League | — | 1997 | Cajundome |
| Lancaster Inferno | National Premier Soccer League | — | 2008 | Hempfield High School |
| Lansdowne Bhoys FC | Cosmopolitan Soccer League | Yonkers | — | — |
| Laredo Heat | USL League Two | Laredo | 2004 | Texas A&M International University Soccer Complex |
| Laredo Honey Badgers | Major Arena Soccer League | — | 2013 | Laredo Energy Arena |
| Las Vegas Lights FC | USL Championship | Las Vegas | 11 August 2017 | Cashman Field |
| Las Vegas Quicksilvers | North American Soccer League | Las Vegas | 1976 | Sam Boyd Stadium |
| Las Vegas Seagulls | American Soccer League | Las Vegas | 1979 | Sam Boyd Stadium |
| Las Vegas Strikers | National Premier Soccer League | — | 2003 | — |
| Lehigh Valley Steam | A-League | Lehigh Valley | 1999 | — |
| Lexington SC | — | Lexington | 2021 | — |
| 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 | — |