| Houston Stars | North American Soccer League | Houston | 1967 | Astrodome |
| Houston Summit | Major Indoor Soccer League | — | 1978 | — |
| Houston Toros | USL League Two | — | 2002 | — |
| Huntsville Fire | Eastern Indoor Soccer League | — | 1997 | Von Braun Center |
| Huracán FC de Caguas | Puerto Rico Soccer League | Caguas | 1991 | Parque Yldefonso Solá Morales |
| Icon FC | American Soccer League | — | 2010 | — |
| Idaho Wolves | National Premier Soccer League | — | 2004 | — |
| IFC Wild Bills | M*League Division 1 | — | 2007 | Oleai Sports Complex |
| Illinois Piasa | Major Arena Soccer League | — | 2007 | — |
| IMG Academy Bradenton | USL League Two | Bradenton | 1998 | — |
| Indiana Blaze | USL W-League | — | 1997 | Kuntz Stadium |
| Indiana Invaders | USL League Two | — | 1998 | Indiana Invaders Soccer Complex |
| Indianapolis Braves | National Premier Soccer League | — | 2007 | — |
| Indianapolis Daredevils | — | Indianapolis | 1974 | — |
| Indios USA | — | — | 2007 | Canutillo Stadium |
| Indy Eleven | USL Championship | Indianapolis | 2013 | IU Michael A. Carroll Track & Soccer Stadium |
| Inter Miami CF | Major League Soccer | Miami | January 29, 2018 | Chase Stadium |
| Inter Nashville FC | National Premier Soccer League | Nashville | — | — |
| Isabela Soccer Club | Liga Nacional de Fútbol de Puerto Rico | — | 2011 | — |
| Jackson Chargers | USL League Two | Jackson | 1995 | — |
| Jacksonville Armada FC | North American Soccer League | — | 2013 | VyStar Ballpark |
| Jacksonville Cyclones | A-League | — | 1995 | Mandarin High School |
| Jacksonville Tea Men | North American Soccer League | — | 1980 | Gator Bowl Stadium |
| Jersey Falcons | USL League Two | — | 2001 | — |
| Jersey Shore Boca | USL League Two | — | 2003 | Ocean County College |
| Kalamazoo FC | National Premier Soccer League | Kalamazoo | 2015 | — |
| Kalamazoo Kingdom | USL League Two | — | 1996 | — |
| Kalamazoo Outrage | USL League Two | — | 2007 | Loy Norrix High School |
| Kansas City Brass | USL League Two | — | 1997 | — |
| Kansas City Spurs | North American Soccer League | Kansas City | 1967 | Municipal Stadium |
| Kansas Magic | Major Arena Soccer League | — | 2011 | — |
| KC Athletics | United States Adult Soccer Association | — | 2001 | — |
| Kearny Celtic | North Jersey Soccer League | Kearny | 1933 | — |
| Kearny Scots | Eastern Premier Soccer League | Kearny | 1895 | — |
| Keene FC | United Premier Soccer League | — | 2017 | Wanda R. Smith High School |
| Kingston Stockade Football Club | National Premier Soccer League | Kingston | 2015 | Dietz Stadium |
| Kitsap Pumas | USL League Two | Bremerton | 2009 | — |
| Kiwi Soccers | ASFA Soccer League | — | 2010 | National Stadium |
| Knoxville Force | National Premier Soccer League | Knoxville | 2010 | — |
| Kraze United | National Premier Soccer League | — | 2015 | UCF Soccer and Track Complex |
| 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 | — | — |
| Lansing Ignite FC | USL League One | Lansing | October 25, 2018 | Jackson Field |
| Laredo Heat | USL League Two | Laredo | 2004 | Texas A&M International University Soccer Complex |