| Sekai Project | video game publisher, business | Norwalk, Los Angeles | 2007 |
| Selznick International Pictures | film production company, film studio | Los Angeles | 1935 |
| Servant Air | airline | Kodiak | 2003 |
| Sesame Workshop | production company, nonprofit organization | 1 Lincoln Plaza, New York City | May 20, 1968 |
| Shaba Games | business | San Francisco | 1997 |
| Shimmer Women Athletes | business, enterprise | Illinois, Chicago, Berwyn | November 6, 2005 |
| Shiny Entertainment | video game developer, business | Laguna Beach, Newport Beach | 1993 |
| Showtime | production company, film production company, cable channel, specialty channel, subscription television | New York City | July 1, 1976 |
| Shrine Auditorium and Expo Hall | auditorium, function hall, theatre building, movie theater | — | 1925 |
| Shure | business, enterprise | Niles | 1925 |
| Shutterstock | business, enterprise, public company | New York City, Empire State Building | 2003 |
| Sierra Nevada Brewing Company | brewery | Chico | 1980 |
| Sierra Nevada Corporation | business | Sparks | 1963 |
| Signetics | integrated device manufacturer | Sunnyvale | 1961 |
| Silver Lake | business, enterprise | Menlo Park | 1999 |
| Silvergate Capital | savings and loan association, bank, business, public company | La Jolla | 1988 |
| Simon & Schuster | book publisher, publishing house | New York City | 1924 |
| Sinclair Broadcast Group | business, enterprise, public company | Hunt Valley, Cockeysville, Union Valley | 1971 |
| Sinclair Oil Corporation | business, gas station chain | Salt Lake City | May 1, 1916 |
| Six Flags Great Adventure | animal theme park | — | July 1, 1974 |
| Six Flags Over Georgia | theme park | — | 1967 |
| Sizzler | restaurant chain | Mission Viejo | January 27, 1958 |
| Skadden, Arps, Slate, Meagher & Flom | law firm | 1 Manhattan West | 1948 |
| Skybound Entertainment | business | Beverly Hills | 1992 |
| Skydance Animation | animation studio | Santa Monica | March 16, 2017 |
| Skydance Direct-to-Consumer | media company | San Francisco | April 12, 2007 |
| Skydance Media | production company, business | Hollywood | 2006 |
| Skywalker Sound | business, recording studio | Lucas Valley | 1975 |
| SkyWest Airlines | regional airline | St. George | 1972 |
| SLB | business, enterprise, public company, oilfield service company | Houston | 1926 |
| Sledgehammer Games | video game developer | Foster City | 2009 |
| Snap-on | business, public company | Kenosha | 1920 |
| Society of Biblical Literature | organization, open-access publisher, scientific society, learned society | Atlanta | 1880 |
| Soka University of America | private not-for-profit educational institution, higher education institution, school | Aliso Viejo | 2001 |
| Sonos | business, enterprise, public company | Santa Barbara | 2002 |
| Sony Pictures Classics | film production company, film distributor | New York City, Los Angeles | January 1992 |
| Sony Pictures Motion Picture Group | business | Culver City | 1998 |
| SoundHound | music recognition software, enterprise, public company | Santa Clara | September 2005 |
| Southeastern Louisiana University | public educational institution of the United States, university | — | 1925 |
| Southern Company | energy company, business, enterprise, public company | Atlanta | 1945 |
| Southern Illinois University | state university system | — | 1869 |
| Southwestern University | liberal arts college, Colleges That Change Lives, private not-for-profit educational institution | — | 1840 |
| SpaceX | launch service provider, business, public company, aerospace manufacturer | Starbase | March 14, 2002 |
| Spalding | sporting goods manufacturer | Bowling Green | 1876 |
| Specialized Bicycle Components | bicycle manufacturer, business, enterprise | Morgan Hill | 1974 |
| Spectrum Brands | business, enterprise, public company | Middleton | 1906 |
| Sports Reference | business | Philadelphia | December 3, 2007 |
| Springfield Armory | business | Geneseo | 1974 |