| Country | Country name |
| Clipperton Island | conventional long form: none conventional short form: Clipperton Island local long form: none local short form: Ile Clipperton former: sometimes called Ile de la Passion |
| Cocos (Keeling) Islands | conventional long form: Territory of Cocos (Keeling) Islands conventional short form: Cocos (Keeling) Islands |
| Colombia | conventional long form: Republic of Colombia conventional short form: Colombia local long form: Republica de Colombia local short form: Colombia |
| Comoros | conventional long form: Union of the Comoros conventional short form: Comoros local long form: Udzima wa Komori (Comorian); Union des Comores (French); Jumhuriyat al Qamar al Muttahidah (Arabic) local short form: Komori (Comorian); Comores (French); Juzur al Qamar (Arabic) |
| Congo, Democratic Republic of the | conventional long form: Democratic Republic of the Congo conventional short form: DRC local long form: Republique Democratique du Congo local short form: RDC former: Congo Free State, Belgian Congo, Congo/Leopoldville, Congo/Kinshasa, Zaire abbreviation: DRC |
| Congo, Republic of the | conventional long form: Republic of the Congo conventional short form: Congo (Brazzaville) local long form: Republique du Congo local short form: none former: Middle Congo, Congo/Brazzaville, Congo |
| Cook Islands | conventional long form: none conventional short form: Cook Islands former: Harvey Islands |
| Coral Sea Islands | conventional long form: Coral Sea Islands Territory conventional short form: Coral Sea Islands |
| Costa Rica | conventional long form: Republic of Costa Rica conventional short form: Costa Rica local long form: Republica de Costa Rica local short form: Costa Rica |
| Cote d'Ivoire | conventional long form: Republic of Cote d'Ivoire conventional short form: Cote d'Ivoire local long form: Republique de Cote d'Ivoire local short form: Cote d'Ivoire note: pronounced coat-div-whar former: Ivory Coast |
| Croatia | conventional long form: Republic of Croatia conventional short form: Croatia local long form: Republika Hrvatska local short form: Hrvatska former: People's Republic of Croatia, Socialist Republic of Croatia |
| Cuba | conventional long form: Republic of Cuba conventional short form: Cuba local long form: Republica de Cuba local short form: Cuba |