| SC United Bantams | USL League Two | Columbia | 2011 | — |
| SD United | Women's Premier Soccer League | — | 2007 | Torero Stadium |
| Seacoast United Mariners | National Premier Soccer League | — | 2011 | Fitzpatrick Stadium |
| Seacoast United Phantoms | USL League Two | Portsmouth | 1996 | — |
| Seacoast United Phantoms | National Premier Soccer League | Portsmouth | 2010 | Portsmouth High School |
| Seattle Impact | Major Arena Soccer League | — | 2014 | accesso ShoWare Center |
| Seattle SeaDogs | Continental Indoor Soccer League | — | November 1993 | Mercer Arena, Climate Pledge Arena |
| Seattle Sounders | North American Soccer League | Seattle | 11 December 1973 | Memorial Stadium |
| Seattle Sounders | USL First Division, A-League | — | 1994 | Starfire Sports |
| Seattle Sounders FC | Major League Soccer | Seattle | 2009 | Lumen Field |
| Seattle Storm | Western Soccer Alliance | — | 1984 | Memorial Stadium |
| Sevilla FC Puerto Rico | Liga Nacional de Fútbol de Puerto Rico | Juncos | 2006 | Juan Ramón Loubriel Stadium |
| Shawsheen Indians | — | Andover | 1923 | — |
| Shreveport Rafters FC | National Premier Soccer League | Shreveport | 2016 | Independence Stadium |
| Sioux Falls Thunder FC | National Premier Soccer League | — | 2016 | — |
| SoCal SC | — | San Bernardino | 2015 | — |
| SoCal Surf | USL League Two | Carlsbad | 2015 | Army and Navy Academy |
| Sonoma County Sol | National Premier Soccer League | Santa Rosa | 2004 | Casa Grande High School |
| Sonoma County Sol | Women's Premier Soccer League | — | 2005 | — |
| Sound FC | USL League Two | Sumner | 2006 | — |
| Southern California Fusion | National Premier Soccer League | Carlsbad | 2004 | — |
| Southern California Lazers | American Soccer League | Torrance | 1978 | — |
| Southern California Seahorses | USL League Two | La Mirada | 2001 | — |
| Southern Colorado Stars | Premier Arena Soccer League | — | 2007 | Colorado Sports Center |
| Southern Oregon Fuego | National Premier Soccer League | — | 2009 | US Cellular Community Park |
| Spartans FC Puerto Rico | Liga Nacional de Fútbol de Puerto Rico | — | 2008 | — |
| Spokane Black Widows | Women's Premier Soccer League | — | 2010 | Joe Albi Stadium |
| Spokane Shadow | USL League Two | Spokane | 1996 | Joe Albi Stadium |
| Spokane Spiders | USL League Two | — | 2006 | Joe Albi Stadium |
| Spokane Velocity | USL League One | Spokane | 2021 | — |
| Sporting Arizona | National Premier Soccer League | Arizona | 1989 | — |
| Sporting Club Jacksonville | — | — | 30 August 2022 | — |
| Sporting Club Jacksonville men | USL Championship | — | 30 August 2022 | — |
| Sporting Club Jacksonville women | USL Super League | — | 16 May 2023 | — |
| Springfield Demize | USL League Two | Springfield | 2006 | — |
| Springfield Storm | USL League Two | — | 2005 | — |
| St. Louis Busch Seniors | — | St. Louis | 1970 | — |
| St. Louis City SC | Major League Soccer | St. Louis | 20 August 2019 | Energizer Park |
| St. Louis Illusion | Major Arena Soccer League | — | 2008 | — |
| St. Louis Knights | — | St. Louis | 1994 | — |
| St. Louis Kutis S.C. | — | St. Louis | 1947 | — |
| St. Louis Lions | USL League Two | St. Louis | 2006 | — |
| St. Louis Simpkins-Ford | — | St. Louis | 1947 | — |
| St. Louis Stars | National Professional Soccer League | St. Louis | 1966 | Busch Memorial Stadium |
| St. Louis Steamers | Major Indoor Soccer League | St. Louis | 1979 | St. Louis Arena |
| St. Louis Steamers | World Indoor Soccer League | — | 1998 | Enterprise Center |
| St. Louis Storm | Major Indoor Soccer League | — | 13 July 1989 | — |
| St. Petersburg FC | USL League Two | St. Petersburg | — | — |