| Cabot Corporation | business, public company | Boston | 1882 |
| CACI | corporation, public company | Arlington County | July 17, 1962 |
| Caesars Entertainment Corporation | business, enterprise | Las Vegas, Paradise | 1937 |
| Calico | business | San Francisco | September 18, 2013 |
| California Baptist University | church college, private not-for-profit educational institution, university | — | 1950 |
| California Institute of Technology | private not-for-profit educational institution, university | California | 1891 |
| California State Polytechnic University, Pomona | public educational institution of the United States, university | — | 1949 |
| California State University | state university system, university | Long Beach | 1857 |
| California State University San Marcos | public educational institution of the United States, university | — | 1989 |
| California State University, Bakersfield | public educational institution of the United States, university | Bakersfield | 1965 |
| California State University, Chico | public educational institution of the United States, public university | Chico | 1887 |
| California State University, Dominguez Hills | public educational institution of the United States, university | Carson | 1960 |
| California State University, Long Beach | public educational institution of the United States, public university | Long Beach | 1949 |
| California State University, Northridge | public educational institution of the United States, public university | Los Angeles | 1958 |
| California State University, Sacramento | public educational institution of the United States, university | Sacramento | 1947 |
| California State University, Stanislaus | public educational institution of the United States, university | — | 1957 |
| Callaway Golf Company | organization, business, public company | Carlsbad | 1982 |
| Calvin University | church college, private not-for-profit educational institution, university | East Grand Rapids | 1876 |
| Cambridge Analytica | business, enterprise | London | 2014 |
| Campbell University | private not-for-profit educational institution, university | — | 1887 |
| Canadian Solar | business, public company | — | 2001 |
| Canisius University | private not-for-profit educational institution, university | Buffalo | 1870 |
| Cannondale Bicycle Corporation | bicycle manufacturer, brand, business | Bethel | 1971 |
| Cape Air | airline | Hyannis | 1989 |
| Capital Group Companies | business, enterprise | Los Angeles | 1931 |
| Carhartt | business, enterprise | Dearborn | 1889 |
| Carleton College | liberal arts college, private not-for-profit educational institution | Northfield | 1866 |
| Carlson Wagonlit Travel | business | Minneapolis | 1994 |
| CarMax | business, public company | Goochland County | 1993 |
| Carnegie Mellon University | research university, private not-for-profit educational institution, private university | Pittsburgh | 1900 |
| Carnegie Steel Company | enterprise | Pittsburgh | 1892 |
| Carnival Corporation | business, dual-listed company, public company, cruise line | Doral, Southampton, Florida, London, Miami | 1972 |
| Carroll Shelby International | automobile manufacturer | Enterprise | August 17, 1962 |
| Carroll University | liberal arts college, private not-for-profit educational institution, private university | Waukesha | 1846 |
| Cartercar | business, automobile manufacturer | Pontiac | 1905 |
| Case Corporation | brand, business | United States | 1842 |
| Castle Rock Entertainment | television production company, film production company | Beverly Hills | June 19, 1985 |
| Catholic News Service | news agency | — | 1920 |
| Cavedog Entertainment | video game developer | Bothell | 1996 |
| CBGB | nightclub, music venue | — | 1973 |
| CBS | radio network, television network | CBS Building | September 18, 1927 |
| CBS Films | film production company, film distributor | Los Angeles | March 2007 |
| CD Baby | media distributor, independent record label, record label, online music store | Portland | 1997 |
| Cecil H. Green Library | academic library, library building | Stanford | 1919 |
| Celera Corporation | business | Rockville, Alameda | May 1998 |
| Celgene | pharmaceutical company, business, enterprise, public company | Summit | 1986 |
| Cencora | business, enterprise, public company | Chesterbrook | 2001 |
| Charles Scribner's Sons | publishing house | New York City | 1846 |
| Charter Arms | business | Shelton | 1964 |
| Charter Oak State College | public educational institution of the United States, university | — | 1973 |
| Chase Bank | bank, business | New York City | 1799 |
| Chateau Marmont | hotel | — | 1927 |
| Chautauqua Airlines | airline | Indianapolis | 1973 |
| Chegg | dot-com company, technology company, public company | Santa Clara | 2005 |
| Chemical Abstracts Service | information system, publishing house | Columbus | 1907 |
| Chemical Bank | business | Midland, New York City | 1954 |
| Chicago State University | public educational institution of the United States, public university | — | September 2, 1867 |
| Chicago, Burlington and Quincy Railroad | railway company | Chicago | 1856 |
| Chili's | restaurant chain | Coppell | March 13, 1975 |
| Chips and Technologies | business, enterprise | Milpitas | 1985 |
| Christopher Newport University | public educational institution of the United States, university, open-access publisher | — | 1961 |
| CHS Inc. | business, gas station chain, public company | Inver Grove Heights | 1931 |
| Chuck E. Cheese | indoor play space, restaurant chain, pizzeria chain, public company | Irving | May 17, 1977 |
| Church's Texas Chicken | fast food restaurant chain, restaurant chain | Sandy Springs | April 17, 1952 |
| Cinemark | cinema chain, public company | Plano | 1984 |
| Cinematronics | video game developer | El Cajon | 1975 |
| Cinemaware | video game publisher, video game developer | Burlingame | 1986 |
| Cineworld | cinema chain, public company | London | 1995 |
| Circle | dot-com company, business | Boston | October 2013 |
| Cirrus Aircraft Corporation | aerospace manufacturer | Duluth | 1984 |
| Citgo | business, gas station chain | Houston | 1910 |
| Citigroup | global systemically important bank, holding company, business, enterprise, credit institution, public company | 388 Greenwich Street | October 8, 1998 |
| Citizens Financial Group | bank, business, public company | Providence | 1954 |
| Claire's | retail chain | Hoffman Estates, Illinois | 1961 |
| Clarivate | public company | Philadelphia, London | October 3, 2016 |
| Clarkson University | private not-for-profit educational institution, university | — | 1896 |
| Clemson University | research university, public educational institution of the United States, land-grant university, public university | — | 1889 |
| Clinique Laboratories, LLC | cosmetics, business, subsidiary company | New York | 1968 |
| ClubJenna | television production company, pornographic film studio | Scottsdale | 2000 |
| CME Group | stock exchange, business, enterprise, public company | Chicago, London | July 12, 2007 |
| CNN | news website, film production company, specialty channel, cable news in the United States | CNN Center, New York City | June 1, 1980 |
| Coach | business, enterprise, public company | New York City | 1941 |
| Coastal Carolina University | public educational institution of the United States, university | Conway | 1954 |
| Coda Automotive | business, automobile manufacturer | Los Angeles | 2009 |
| Codecademy | open educational resource, Virtual learning environment, website, business | New York City | 2011 |
| CodeGear | business, enterprise | Scotts Valley, California | 2006 |
| Cognizant Technology Solutions | technology company, enterprise, public company | Teaneck | 1994 |
| Cole Haan | business, subsidiary company, brick and mortar | Greenland | 1928 |
| Coleco | brand, business | West Hartford | 1932 |
| Coleman Company | business | Wichita | 1900 |
| Colgan Air | regional airline | Memphis | 1991 |
| College of William & Mary | public educational institution of the United States, public research university | Williamsburg | 1693 |
| Colorado College | liberal arts college, private not-for-profit educational institution | Colorado Springs | 1874 |
| Colorado Fuel and Iron | business | Colorado | — |
| Columbia Pictures | film production company, film distributor | United States, Culver City | 1918 |
| Columbia University Press | book publisher, nonprofit organization, university press | New York City | 1893 |
| Columbia University Vagelos College of Physicians and Surgeons | graduate school, university, medical school | New York City | 1767 |
| Columbus Museum of Art | nonprofit organization, art museum, movie theater | Columbus | 1931 |
| Comcast | telecommunications company, business, enterprise, public company | Philadelphia | June 28, 1963 |
| CommuteAir | regional airline | Westlake | 1989 |
| Complex | magazine, business | New York City | 2002 |
| Concord | record company, business | Beverly Hills | 1973 |
| Conexant | business, enterprise | Irvine | 1999 |
| Connecticut College | liberal arts college, private not-for-profit educational institution, school | — | 1911 |
| ConocoPhillips | business, enterprise, public company | Houston | 1875 |
| Conrail | railway company | Philadelphia | April 1, 1976 |
| Consol Energy | business, enterprise, public company | Pittsburgh | 1991 |
| Constellation Brands | business, company, public company | Victor | 1945 |
| Continental Airlines | airline | Chicago, Denver, Houston, El Paso, Los Angeles | 1934 |
| Continental Express | airline | Houston | 1986 |
| Convair | launch service provider, aerospace manufacturer | San Diego | 1943 |
| Cooper Tire & Rubber Company | business, enterprise, public company | Findlay | 1926 |
| Cooper Union | college, private not-for-profit educational institution | — | 1859 |
| Coors Brewing Company | brewery, business | Golden | 1873 |
| Cornell University | research university, private not-for-profit educational institution, land-grant university, sun grant institution, private university | Ithaca | 1865 |
| Cornell University Press | book publisher, university press | Ithaca | 1869 |
| Corning Inc. | organization, business, enterprise, public company | Corning | 1851 |
| Corteva | business, public company | Washington, D.C. | March 15, 2018 |
| Cosmopolitan of Las Vegas | casino, hotel | — | April 2004 |
| Costco | business, retail chain, enterprise, public company | Issaquah | 1983 |
| Coty | business, enterprise, public company | New York City | 1904 |
| CouchSurfing | hospitality service, website, business | San Francisco | April 2, 2003 |
| 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 |
| Courtyard by Marriott | hotel chain | Bethesda | 1983 |
| CoverGirl | brand, business | Maryland | 1961 |
| Cox Enterprises | enterprise | Atlanta | 1898 |
| Crave Entertainment | video game developer | Newport Beach | 1997 |
| Cray | public company | Seattle | 1972 |
| Crayola LLC | business, enterprise | Forks Township | 1885 |
| Creative Commons | nonprofit organization, publishing house, author | Mountain View | January 15, 2001 |
| Creative Micro Designs | business | East Longmeadow | 1987 |
| Credo Reference | business | Boston | 1999 |
| Cricket Wireless | mobile virtual network operator, telecommunications company, business, mobile phone store chain | San Diego | 1999 |
| CrimethInc. | collective, group of humans, publishing house | — | 1996 |
| Crocs, Inc. | retail chain, brick and mortar, public company | Longmont | 2002 |
| Crosley | business, automobile manufacturer | Cincinnati | 1937 |
| CrossFit | hobby, business | Santa Cruz | 2000 |
| Crown Castle International Corp. | organization, real estate investment trust, company, public company | Houston | January 1, 1994 |
| Cruise/Wagner Productions | film production company | Los Angeles | July 1992 |
| 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 |
| Cryptic Studios | video game developer | Los Gatos | June 2000 |
| Crystal Dynamics | video game developer | Redwood City | 1992 |
| CSX Corporation | organization, business, enterprise, public company | CSX Transportation Building | November 1, 1980 |
| Culinary Institute of America | private not-for-profit educational institution, cooking school, private university | Hyde Park, New Haven, Hyde Park | May 22, 1946 |
| Cummins | business, public company | Columbus | 1919 |
| CUNY Graduate School and University Center | graduate school, public educational institution of the United States, research institute, open-access publisher | New York City | 1961 |
| Currier and Ives | male duo, business | New York City | 1835 |
| Curtiss-Wright | holding company, business, public company, aerospace manufacturer | Charlotte | 1929 |
| CVS Health | organization, business, enterprise, public company | Rhode Island, Woonsocket | 1963 |
| Cyan Worlds | privately held company, video game developer, business | Wilmington, Mead | 1987 |
| Cygnus Solutions | business | — | November 13, 1989 |
| Cyrix | business, public company | Richardson | 1988 |