| Chicago Mercantile Exchange | futures exchange, business | Chicago | 1898 |
| Chicago The Musical Ambassador Theater | Broadway theatre, theatre building, movie theater | — | February 11, 1921 |
| Chicago, Rock Island and Pacific Railroad | railway company, business, transport company | Chicago | 1866 |
| Chick-fil-A | fast food restaurant chain | Georgia | 1946 |
| Chikara | business, professional wrestling promotion | Philadelphia | 2002 |
| Chili's | restaurant chain | Coppell | March 13, 1975 |
| Chipotle Mexican Grill | restaurant chain, organization, business, enterprise, public company | Denver, Newport Beach | July 13, 1993 |
| Choate Rosemary Hall | boarding school, organization | Wallingford | 1890 |
| Choice Hotels | hotel chain, business, public company | Rockville, Silver Spring | 1939 |
| Christopher Newport University | public educational institution of the United States, university, open-access publisher | — | 1961 |
| Chuck E. Cheese | indoor play space, restaurant chain, pizzeria chain, public company | Irving | May 17, 1977 |
| Church & Dwight | business, enterprise, public company | Ewing Township | 1846 |
| Church's Texas Chicken | fast food restaurant chain, restaurant chain | Sandy Springs | April 17, 1952 |
| Cinemaware | video game publisher, video game developer | Burlingame | 1986 |
| Circle | dot-com company, business | Boston | October 2013 |
| Circuit City Stores | business, enterprise | Richmond | 1984 |
| Circus Circus Las Vegas | casino, hotel | — | October 18, 1968 |
| Cisco | business, enterprise, public company | San Jose | 1984 |
| Citadel LLC | business, unlisted public company, company, financial services | Miami | 1990 |
| Citgo | business, gas station chain | Houston | 1910 |
| Citibank | bank, business, financial institution, credit institution | Sioux Falls, New York City | 1865 |
| Citizens Financial Group | bank, business, public company | Providence | 1954 |
| City College of New York | public educational institution of the United States, higher education institution | New York City | 1847 |
| Clarivate | public company | Philadelphia, London | October 3, 2016 |
| Clark Atlanta University | historically black college or university, private not-for-profit educational institution, private university | — | September 19, 1865 |
| Clark University | liberal arts college, Colleges That Change Lives, private not-for-profit educational institution, private university | Worcester | 1887 |
| Clarkson University | private not-for-profit educational institution, university | — | 1896 |
| CLS Group | business | New York | 2002 |
| ClubJenna | television production company, pornographic film studio | Scottsdale | 2000 |
| Coastal Carolina University | public educational institution of the United States, university | Conway | 1954 |
| CodeGear | business, enterprise | Scotts Valley, California | 2006 |
| Cognex Corporation | business, public company | Natick | 1981 |
| Cold Spring Harbor Laboratory | nonprofit organization, research institute, academic publisher | — | 1890 |
| Cole Haan | business, subsidiary company, brick and mortar | Greenland | 1928 |
| Coleco | brand, business | West Hartford | 1932 |
| College of the Holy Cross | liberal arts college, private not-for-profit educational institution, university | Worcester | 1843 |
| Collins Aerospace | defense contractor, aerospace manufacturer | Charlotte | 2018 |
| Colorado College | liberal arts college, private not-for-profit educational institution | Colorado Springs | 1874 |
| Colorado State University | public educational institution of the United States, land-grant university, public research university | — | 1870 |
| Columbia Pictures | film production company, film distributor | United States, Culver City | 1918 |
| Columbia Sportswear Company | business, enterprise, brick and mortar, public company | Cedar Mill | 1938 |
| Columbia University Graduate School of Journalism | graduate school, academic department, journalism school | New York City | 1912 |
| Columbia University Press | book publisher, nonprofit organization, university press | New York City | 1893 |
| Comair | airline, defunct organization, wholly owned subsidiary | Erlanger | 1977 |
| Combustion Engineering | business | Stamford | 1912 |
| Comcast | telecommunications company, business, enterprise, public company | Philadelphia | June 28, 1963 |
| Common Crawl | dot-com company, nonprofit organization | — | 2008 |
| Compaq | technology company, business, enterprise | Houston | February 16, 1982 |