C
| Name | Established | Location |
| Cagigal Observatory | 1888 | Caracas, Venezuela |
| Cagliari Observatory | 1899 | Cagliari, Sardinia |
| Calar Alto Observatory | 1975 | Almería, Spain |
| Caltech Submillimeter Observatory | Mauna Kea, Hawaii, USA | |
| Canopus Hill Observatory | Hobart, Tasmania, Australia | |
| Capilla Peak Observatory | Albuquerque, New Mexico, USA | |
| Capodimonte Observatory | 1812 | Naples, Italy |
| Carter Observatory | 1937 | Wellington, New Zealand |
| Catania Astrophysical Observatory | Catania, Italy | |
| Celestial Observatory | Russellville, Arkansas, USA | |
| Centennial Observatory | 2004 | Twin Falls, Idaho, USA |
| Cerro Armazones Observatory | 1995 | Atacama Desert, Chile |
| Cerro Tololo Inter-American Observatory | 1962 | Atacama Desert, Chile |
| Cerro Pachón Observatory | 2000 | Atacama Desert, Chile |
| Chabot Space & Science Center | 1883 | Oakland, California, USA |
| Chamberlin Observatory | 1890 | Denver, Colorado, USA |
| Changchun Astronomical Observatory | Changchun, Jilin Province, China | |
| Chandra X-ray Observatory | 1999 | Highly eccentric Earth orbit |
| Chico Community Observatory | Chico, California, USA | |
| Cincinnati Observatory | 1843 | Cincinnati, Ohio, USA |
| City Observatory, Edinburgh | 1818 | Edinburgh, Scotland |
| Clarke Observatory | 1897 / 1923 | Dunkirk, New York / Alliance, Ohio, USA |
| Coats Observatory | 1883 | Paisley, Scotland |
| Coit Observatory | Boston, Massachusetts, USA | |
| Collins Observatory | 2003 | Corning, New York, USA |
| Collm Observatory | Leipzig, Germany | |
| Colombo University Observatory | 1920's | Colombo, Sri Lanka |
| Compton Gamma-Ray Observatory (defunct) | 1991–2000 | Low earth orbit |
| Concordia College Observatory | Moorhead, Minnesota, USA | |
| Consell Observatory | 1987 | Majorca, Spain |
| Copenhagen University Observatory | 1861 | Copenhagen, Denmark |
| Cordell–Lorenz Observatory | Sewanee, Tennessee, USA | |
| COROT | 2006 | Polar orbit |
| Cosmic Background Imager (CBI) | 1999 | Llano de Chajnantor Observatory, Chile |
| Côte d'Azur Observatory | 1988 | France |
| Crane Observatory | Topeka, Kansas, USA | |
| Crawford Observatory | 1880 | Cork, Ireland |
| Creighton University Observatory (defunct) | 1886–1955 | Omaha, Nebraska, USA |
| Crimean Astrophysical Observatory | 1945 | Ukraine |
| Črni Vrh Observatory | 1975 | Idrija, Slovenia |
| Cupillari Observatory | La Plume, Pennsylvania, USA | |
| CUASAR, University of Valencia observatory | 2008 | Aras de los Olmos, Valencia, Spain |
| Custer Observatory | 1927 | Southold, New York, USA |
Read more about this topic: List Of Astronomical Observatories