| Compass Airlines | airline | Minneapolis–Saint Paul International Airport | 2006 |
| Conair Corporation | business, enterprise | East Windsor Township | 1959 |
| Concentrix | business | Fremont | 2004 |
| Concord | record company, business | Beverly Hills | 1973 |
| Conexant | business, enterprise | Irvine | 1999 |
| Conrail | railway company | Philadelphia | April 1, 1976 |
| Consol Energy | business, enterprise, public company | Pittsburgh | 1991 |
| Continental Express | airline | Houston | 1986 |
| Continental Micronesia | airline | Tamuning | 1968 |
| Cooper Union | college, private not-for-profit educational institution | — | 1859 |
| Coors Brewing Company | brewery, business | Golden | 1873 |
| Cord Automobile | business | United States | 1929 |
| CoreCivic | business, enterprise, public company | Nashville | 1983 |
| CoreWeave | business, enterprise | Roseland | 2017 |
| CosMc's | fast food restaurant | Chicago | December 7, 2023 |
| Coty | business, enterprise, public company | New York City | 1904 |
| CouchSurfing | hospitality service, website, business | San Francisco | April 2, 2003 |
| Council on Vertical Urbanism | publishing house, organization | Illinois Institute of Technology | 1969 |
| Courant Institute School of Mathematics, Computing, and Data Science | academic institute, faculty, higher education institution, organization | — | 1935 |
| Coursera | massive open online course provider, website, education company, public company | Mountain View | 2012 |
| Cracker Barrel | restaurant chain, public company | Lebanon | September 19, 1969 |
| Crackle | business, video streaming service, streaming service | Culver City | July 2007 |
| Cray | public company | Seattle | 1972 |
| CRC Press | book publisher, publishing house | Boca Raton | 1903 |
| Creative Artists Agency | talent agency, company | Century City | 1975 |
| Creative Micro Designs | business | East Longmeadow | 1987 |
| Credo Reference | business | Boston | 1999 |
| CrimethInc. | collective, group of humans, publishing house | — | 1996 |
| Cross Creek Pictures | film production company | Los Angeles | 2009 |
| CrowdStrike | business, public company | Austin | August 29, 2011 |
| Crown Castle International Corp. | organization, real estate investment trust, company, public company | Houston | January 1, 1994 |
| Crumbl Cookies | restaurant chain | Lindon | 2017 |
| Crunchbase | data set, website, business, online database | San Francisco | July 2007 |
| Crunchyroll | application software, video streaming service, Internet audio-visual programming service provider, mobile app, streaming service, Internet television | San Francisco | May 14, 2006 |
| CSX Transportation | railway company | — | July 1, 1986 |
| Culinary Institute of America | private not-for-profit educational institution, cooking school, private university | Hyde Park, New Haven, Hyde Park | May 22, 1946 |
| Currier and Ives | male duo, business | New York City | 1835 |
| Curtis Institute of Music | conservatory, private not-for-profit educational institution, college of music | — | 1924 |
| Cushman & Wakefield | business, enterprise, public company | New York City | 1917 |
| CVS Pharmacy | business, pharmacy chain | Woonsocket | 1963 |
| Cyan Worlds | privately held company, video game developer, business | Wilmington, Mead | 1987 |
| Cypress Semiconductor | business | San Jose | 1982 |
| Cyrix | business, public company | Richardson | 1988 |
| D'Addario | business | Farmingdale | 1973 |
| Da Capo Press | publishing house | Boston | 1964 |
| Dag Hammarskjöld Library | library, library building | — | 1946 |
| Dairy Queen | fast food restaurant chain, restaurant chain, ice cream parlor chain | Bloomington, Edina | June 22, 1940 |
| Dallas Semiconductor | business | Dallas | February 1, 1984 |