| Springfield College | private not-for-profit educational institution | Springfield | 1885 |
| Sprint Corporation | mobile network operator, business, enterprise, public company | Overland Park | 1899 |
| Squarespace | commercial organization, public company | New York City | 2003 |
| SRAM Corporation | bicycle part manufacturing company | Chicago | 1987 |
| SSC North America | business, enterprise, automobile manufacturer | West Richland | 1999 |
| St. Ambrose University | private not-for-profit educational institution, seminary, university, building | — | 1882 |
| St. Cloud State University | public educational institution of the United States, university | St. Cloud | 1869 |
| St. Lawrence University | private not-for-profit educational institution, liberal arts college in the United States, private university | Canton | 1856 |
| Standard Oil of Ohio | business, gas station chain | Cleveland | 1911 |
| Stanford Graduate School of Business | business school, graduate school, organization | — | 1925 |
| Stanley Black & Decker | business, public company | New Britain | 1843 |
| Stanley Motor Carriage Company | automobile manufacturer | Newton | 1902 |
| Staples Inc. | business, retail chain, enterprise, public company | Framingham | 1986 |
| Starbucks | café chain | Seattle | March 30, 1971 |
| Stardust Resort and Casino | skyscraper, casino, hotel, music venue | — | 1958 |
| Starkey Hearing Technologies | business | Eden Prairie | 1967 |
| Starwood | business, enterprise, public company | White Plains | 1930 |
| State Farm Insurance | business, car insurance company, life insurance company, property insurance company | Bloomington | 1922 |
| State Street Corporation | global systemically important bank, business, enterprise, credit institution, public company | Boston | 1792 |
| State University of New York at Purchase | public educational institution of the United States, university | — | 1967 |
| Steak 'n Shake | restaurant chain, business, enterprise | Indianapolis | 1934 |
| Steelcase | business, public company | Grand Rapids | 1912 |
| Stepan Company | business, public company | Northfield | 1932 |
| Sterling Memorial Library | academic library, library building | — | 1930 |
| Sterling Trucks | truck manufacturer, commercial vehicle manufacturer | Redford | 1997 |
| Stetson University | private not-for-profit educational institution, university | DeLand | 1883 |
| Steve Jackson Games | tabletop role-playing game publisher, board game publishing company | Austin | 1980 |
| Stockton University | public educational institution of the United States, university | — | 1969 |
| Stony Brook University | research university, public educational institution of the United States, public university | Stony Brook University | September 16, 1957 |
| Strand Bookstore | book vendor | — | 1927 |
| Strategic Simulations | video game publisher, video game developer, business, enterprise | Sunnyvale | 1979 |
| Strategy | software company, business, public company | Tysons | 1989 |
| Stratolaunch Systems | business, enterprise | Montgomery, Seattle | 2011 |
| Stripe | payment processor, business | San Francisco, South San Francisco | 2010 |
| Stüssy, Inc. | business, enterprise | Irvine | 1980 |
| Substack | website, publishing platform, business, podcast hosting service, enterprise, service | — | November 29, 2017 |
| Sucker Punch Productions | video game developer | Bellevue | October 1997 |
| Sullivan & Cromwell | law firm | New York City | 1879 |
| Sun Microsystems | software company, academic spin-off, business, public company | Santa Clara | February 24, 1982 |
| Sunkist Growers | business, enterprise | Los Angeles | August 29, 1893 |
| Sunoco | oil company, business, gas station chain, enterprise | Dallas | 1886 |
| Supergiant Games | video game publisher, video game developer | San Jose | 2009 |
| SurveyMonkey | customer experience management, software as a service, service on Internet, trademark, enterprise feedback management, online survey service, market research and public opinion polling, business, Customer experience systems, public company, market research | San Mateo | 1999 |
| Swarthmore College | liberal arts college, private not-for-profit educational institution | — | 1864 |
| Swift Engineering | business, enterprise, aerospace manufacturer | San Clemente | 1983 |
| Symbolics | business | Concord | 1979 |
| Synaptics | technology company, business, enterprise | Santa Clara | 1986 |
| Synopsys | business, enterprise, public company | Mountain View | 1986 |