| 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 |