- Calénnawn by René Uittenbogaard (0 features)
- CALS Average Feature Values by Kiriyow (145 features)
- Cannic by Nikhil Sinha (99 features)
- Cardhic, Common by Sectori (119 features)
- Carrajina by A Walker Scott (57 features)
- Caryatic by Justin Mansfield (60 features)
- Catralian by Gabriel Wysong (3 features)
- Ccharthii by Colz (113 features)
- Celdirin by Eyowa (136 features)
- Celestial by Enrique Gamez (82 features)
- Celíminé by Logan Kearsley (133 features)
- Celinese by A. Ayres (145 features)
- Cenemanian by El Imiradu (30 features)
- Centaurian by Enrique Gamez (75 features)
- Cenyani by Adam Heurlin (139 features)
- Cerstan by Doranwen (73 features)
- Chagrandi by Milora Stasievic (136 features)
- Chamanar by Ave94 (50 features)
- Charlchrist Spoken Language by - (0 features)
- Charlchrist Spoken Launguage by Charlie Gilchrist (0 features)
- Cheklomino by eurasianon (77 features)
- Cherun by Nortaneous (15 features)
- Chesterian by Liam (3 features)
- Chharang by Bryony (93 features)
- Chlouvanem by lilie21 (141 features)
- Choch Gwurx by drwmcn (38 features)
- Cholnish by Andre (117 features)
- Choskchsskiirt by W (0 features)
- Choton by Pascal Kramm (112 features)
- Cialmi by teeohbeewye (126 features)
- Cikap by phi2dao (143 features)
- Cirena by He/Sidhe (28 features)
- City Speech by iewi (76 features)
- Clarnenamerin by Udrihel (11 features)
- Classical Airumali by Carl Miller, Jr. (20 features)
- Classical Arithide by Eugene Oh (135 features)
- Classical Rossan by Colleen (68 features)
- Classical Uraki by k1234567890y (102 features)
- clikli dialect by k1234567890y (74 features)
- Cljek Pikay by aarginost (34 features)
- Clofabian by IlL (67 features)
- Common Honey by The Common Honey Tribe (110 features)
- Common Western Hakessian by Michael M. Goessler (37 features)
- Coral Reef language by k1234567890y (94 features)
- Cropish by titusflavius (20 features)
- Cruckeny by Dillon Hartwig (142 features)
- Cwengaer by Fauxlosophe (130 features)
- Cylvian by Enrique Gamez (66 features)
- Cyraceí by me (53 features)