| San Francisco Nighthawks | Women's Premier Soccer League | San Francisco | 1995 | Kezar Stadium |
| San Francisco Seals | A-League | San Francisco | 1992 | Negoesco Stadium |
| San Francisco Stompers FC | National Premier Soccer League | Hayward | 2012 | Pioneer Stadium |
| San Francisco Vikings Soccer Club | — | San Francisco | 1922 | — |
| San Gabriel Valley Highlanders | USL League Two | Glendale | 1997 | — |
| San Jose CyberRays | Women's United Soccer Association | San Jose | 2001 | CEFCU Stadium |
| San Jose Earthquakes | Major League Soccer | San Jose | 1995 | PayPal Park, Stevens Stadium |
| San Jose Earthquakes | North American Soccer League | San Jose | December 11, 1973 | — |
| San Jose Earthquakes U23 | USL League Two | — | 2013 | — |
| San Jose Frogs | USL League Two | San Jose | 2005 | — |
| San Jose Grizzlies | Continental Indoor Soccer League | — | 1993 | SAP Center |
| San Juan United | Liga Nacional de Fútbol de Puerto Rico | — | 2008 | — |
| Santa Ana Winds FC | National Premier Soccer League | Santa Ana | 2009 | Santa Ana Stadium |
| Santa Barbara Condors | — | Santa Barbara | 1977 | — |
| Santa Barbara Sky FC | — | Santa Barbara | 2022 | — |
| Santa Cruz County Breakers | National Premier Soccer League | Santa Cruz | 2007 | — |
| Sarasota Paradise | USL League One | Lakewood Ranch | November 19, 2022 | — |
| Saturn FC | National Premier Soccer League | — | 2009 | — |
| Savannah Rug Ratz | Eastern Indoor Soccer League | — | 1997 | Savannah Civic Center |
| 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 | 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 |
| Shreveport Rafters FC | National Premier Soccer League | Shreveport | 2016 | Independence Stadium |
| Sioux Falls Spitfire | USL League Two | — | 2001 | O'Gorman Catholic High School |
| 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 | — |
| 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 West Virginia King's Warriors | USL League Two | — | 2012 | East River Soccer Complex |
| 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 | — |