| Civil war in Tajikistan | Civil-military operations | Civilian |
| Civilian control of the military | Civilisées | Civilization |
| Civilization (series) | Civilization V | Civilization V: Brave New World |
| Civilized core | Civitas Popthensis | Cizre |
| CJ Parker (wrestler) | CJCUC | CKM matrix |
| Cl | Claddagh ring | Cladding (construction) |
| Cladistics | Cladium mariscus | Cladobranchia |
| Cladocera | Cladorhynchus | Cladorhynchus leucocephalus |
| Cladosporium | Cladrastis kentukea | Claflin, Kansas |
| Claiborne County, Tennessee | Claiborne Parish, Louisiana | Claim rights and liberty rights |
| Claimed moons of Earth | Clair Cameron Patterson | Claire City, South Dakota |
| Claire Danes | Claire Etcherelli | Claire Holt |
| Claire Lee Chennault | Claire Redfield | Clairmarais |
| Clairton, Pennsylvania | Clam AntiVirus | Clam Falls, Wisconsin |
| Clam Lake Township, Michigan | Clam Union Township, Michigan | Clamator |
| Clamator coromandus | Clamator glandarius | Clamator jacobinus |
| ClamAV | CLAMP | ClamWin |
| ClamWin Antivirus | Clancy Brown | Clandestine abuse |
| Clanga clanga | Clanga pomarina | Clangula hyemalis |
| Clans, Alpes-Maritimes | Clapper bridge | Clapperboard |
| Clara Barton | Clara Basiana | Clara Bow |
| Clara City, Minnesota | Clara Janés | Clara Khoury |
| Clara Zetkin | Clarabelle Cow | Clarín (Argentine newspaper) |
| Clare Boothe Luce | Clare County, Michigan | Clare, Iowa |
| Clare, Michigan | Clare, New York | Claremont, Illinois |
| Claremont, Minnesota | Claremont, New Hampshire | Claremont, North Carolina |
| Claremont, South Dakota | Claremont, Virginia | Claremore, Oklahoma |
| Clarence (2014 TV series) | Clarence Acuña | Clarence Day |
| Clarence Goodson | Clarence King | Clarence L. Johnson |
| Clarence Nash | Clarence Seedorf | Clarence Township, Michigan |
| Clarence Williams III | Clarence, Iowa | Clarence, New York |
| Clarendon Hills, Illinois | Clarendon Township, Michigan | Clarendon, Arkansas |
| Clarendon, New York | Clarendon, Quebec | Clarendon, Texas |
| Clarendon, Vermont | Clarias batrachus | Clariden |
| Clariidae | CLARINASE | Clarinda, Iowa |
| Clarinet | Clarington, Ohio | Clarion County, Pennsylvania |
| Clarion, Iowa | Clarissa, Minnesota | Clarithromycin |
| Clark County, Indiana | Clark County, Wisconsin | Clark Duke |
| Clark Gable | Clark International Airport | Clark Johnson |
| Clark L. Hull | Clark Township, Michigan | Clark, South Dakota |
| Clarkdale, Arizona | Clarke Carlisle | Clarke County, Alabama |
| Clarke's three laws | Clarkedale, Arkansas | Clarkesville, Georgia |
| Clarkfield, Minnesota | Clarkia amoena | Clarks Grove, Minnesota |
| Clarks Hill, Indiana | Clarks, Nebraska | Clarksburg, Massachusetts |
| Clarksburg, Ohio | Clarksburg, Tennessee | Clarksburg, West Virginia |
| Clarksdale, Mississippi | Clarkson, Kentucky | Clarkson, New York |
| Clarkston, Georgia | Clarkston, Michigan | Clarkston, Utah |
| Clarkston, Washington | Clarkstown, New York | Clarksville City, Texas |
| Clarksville, Allegany County, New York | Clarksville, Arkansas | Clarksville, Indiana |
| Clarksville, Iowa | Clarksville, Michigan | Clarksville, New Hampshire |
| Clarksville, Ohio | Clarksville, Tennessee | Clarksville, Texas |
| Clarksville, Virginia | Clarkton, North Carolina | Clarno, Wisconsin |
| Clarques | Clash of Civilizations | Clash of Clans |
| Clash of clans | Clash of Loyalties | Clash of the Titans (2010 film) |
| Clasper | Class (biology) | Class (computer programming) |
| Class conflict | Class consciousness | Class discrimination |
| Class in Marxist theory | Class struggle | Classes of computers |
| Classful network | Classic car | Classic metal |
| Classical antiquity | Classical architecture | Classical compound |
| Classical conditioning | Classical electromagnetism | Classical electron radius |
| Classical element | Classical liberalism | Classical limit |
| Classical mechanics | Classical order | Classical physics |
| Classical planet | Classicism | Classics |
| Classification of finite simple groups | Classification of mental disorders | Classification society |
| Classified advertising | Classless Inter-Domain Routing | Classroom |
| Classroom design | Clathrate hydrate | Clatonia, Nebraska |
| Clatskanie, Oregon | Claude Adrien Helvétius | Claude Étienne Savary |
| Claude Bernard | Claude Berri | Claude Cahen |
| Claude Chevalley | Claude Cohen-Tannoudji | Claude Dornier |
| Claude Etienne Savary | Claude Faraggi | Claude Frollo |
| Claude Gaspard Bachet de Méziriac | Claude Giroux | Claude Henri de Rouvroy, comte de Saint-Simon |
| Claude Joseph Rouget de Lisle | Claude Lévi-Strauss | Claude Le Roy |
| Claude Louis Berthollet | Claude Makélélé | Claude Nicolas Ledoux |
| Claude Puel | Claude Reignier Conder | Claude Rich |
| Claude Saumaise | Claude Shannon | Claude Simon |
| Claude, Texas | Claude-Arnaud Rivenet | Claude-Étienne Savary |
| Claude-Etienne Savary | Claude-Louis Navier | Claudette Colbert |
| Claudette Colvin | Claudia Cardinale | Claudia Ciesla |
| Claudia Pechstein | Claudia Schiffer | Claudio Bellucci |
| Claudio Biaggio | Claudio Bravo (footballer) | Claudio Caniggia |
| Claudio García | Claudio Gentile | Claudio Husaín |
| Claudio López (footballer) | Claudio Marchisio | Claudio Morel Rodríguez |
| Claudio Pizarro | Claudio Puglisi | Claudio Ranieri |
| Claudio Reyna | Claudio Sánchez-Albornoz | Claudio Sánchez-Albornoz y Menduiña |
| Claudio Suárez | Claudio Terzi | Claudiu Bleonț |
| Claudius | Claudius Bombarnac | Claudius Gothicus |
| Claudius James Rich | Claudius Salmasius | Claus Bo Larsen |
| Claus Jensen | Claus von Stauffenberg | Clauseneae |
| Clauseninae | Clausius–Clapeyron relation | Claussenomyces atrovirens |
| Claustrum | Clavam | Claverack, New York |
| Claviceps | Claviceps africana | Claviceps annulata |
| Claviceps cinerea | Claviceps fusiformis | Claviceps glabra |
| Claviceps inconspicua | Claviceps litoralis | Claviceps lutea |
| Claviceps pallida | Claviceps setulosa | Claviceps sorghi |
| Claviceps sorghicola | Claviceps viridis | Claviceps zizaniae |
| Clavicipitaceae | Clavicle | Clavicle fracture |
| Clavigo (play) | Clavipectoral fascia | Clavulanic acid |
| Claw | Clawson, Michigan | Clawson, Utah |
| Claxton, Georgia | Clay | Clay Banks, Wisconsin |
| Clay Center, Kansas | Clay Center, Ohio | Clay City, Illinois |
