S
| Name | Established | Location |
| San Fernando Observatory (SFO) | 1976 | Sylmar, California, USA |
| Sayan Spectrographic Cosmic Ray Complex | Irkutsk, Russia | |
| SFA Observatory | 1976 | Nacogdoches, Texas, USA |
| Sagamore Hill Radio Observatory | 1963 | Hamilton, Massachusetts, USA |
| Shattuck Observatory | 1854 | Hanover, New Hampshire, USA |
| Seven Hills Observatory | 1996 | Kearney, Nebraska, USA |
| Shamakhi Astrophysical Observatory | 1958 | Shamakhi, Azerbaijan |
| Shanghai Astronomical Observatory | 1962 | Shanghai, China |
| Sherzer Observatory | 1878 | Ypsilanti, Michigan, USA |
| Sheshan Astronomical Observatory | 1900 | Shanghai, China |
| Siding Spring Observatory | Siding Spring, New South Wales, Australia | |
| Sierra Nevada Observatory | 1874 | Sierra Nevada, Spain |
| Silesian Planetarium and Astronomical Observatory | 1955 | Chorzów / Katowice, Silesia, Poland |
| Simeiz Observatory | Simeiz, Crimea, Ukraine | |
| Skalnaté Pleso Observatory | 1953 | Vysoké Tatry, Slovakia |
| Skinakas Observatory | 1984 | Crete, Greece |
| Skylab | 1973 | low Earth orbit; re-entered in 1979 |
| Smith Observatory | 1880s | Beloit, Wisconsin, USA |
| Smithsonian Astrophysical Observatory | 1890 | Cambridge, Massachusetts, USA |
| Sola Fide Observatory | Austin, Minnesota, USA | |
| Solar and Heliospheric Observatory (SOHO) | 1996 | Earth–Sun L1 point |
| Solar Space Telescope | 2009 | 709 km SSO; life: 3 years |
| Sommers–Bausch Observatory | 1949 | Boulder, Colorado, USA |
| Sonnenborgh Observatory | 1853 | Utrecht, Netherlands |
| Sonoma State Observatory | 1976 | Rohnert Park, California, USA |
South African Astronomical Observatory
|
|
Observatory, Cape Town, South Africa
|
| Southern Astrophysical Research Telescope (SOAR) | 2004 | Cerro Pachón, Chile |
| South Pole Telescope | 2007 | Antarctica |
| Space Hard X-Ray Modulation Telescope | 2010 | 550 km LEO |
| Spanish National Observatory | 1790 | (Spain) |
| Special Astrophysical Observatory of the Russian Academy of Sciences | Caucasus Mountains, Russia | |
| Sperry Observatory | 1967 | Cranford, New Jersey, USA |
| Spitzer Space Telescope | 2003 | Heliocentric orbit |
| Springfield Observatory | 1968 | Springfield, Massachusetts, USA |
| Sproul Observatory | Swarthmore, Pennsylvania, USA | |
| Stardome Observatory | 1967 | Auckland, North Island, New Zealand |
| Starkenburg Observatory | 1970 | Heppenheim, Germany |
| Štefánik's Observatory | 1928 | Prague, Czech Republic |
Steward Observatory
|
1916 | Tucson, Arizona, USA |
| Stjerneborg | 1581 | Hven, Sweden |
| Stockholm Observatory | 1749 | Stockholm, Sweden |
| Stokesville Observatory | Virginia, USA | |
| Stonyhurst Observatory | 1838 | Lancashire, England |
| Strasbourg Observatory | 1881 | Strasbourg, France |
| Stratospheric Observatory for Infrared Astronomy | 2006 | Boeing 747SP airliner |
| Stull Observatory | 1966 | Alfred, New York, USA |
| Stuttgart Observatory | 1920 | Stuttgart, Germany |
| Submillimeter Array | Mauna Kea, Hawaii, USA | |
| Sudbury Neutrino Observatory | 1999 | Sudbury, Ontario, Canada |
| Sunriver Observatory | Sunriver, Oregon, USA | |
| Swift Gamma-Ray Burst Mission | 2004 | Low Earth orbit |
| Sydney Observatory | 1858 | Sydney, Australia |
Read more about this topic: List Of Astronomical Observatories