| Abbreviation | Definition |
|---|---|
| CGAA | Cottage Grove Athletic Association |
| CHAA | Coastal Homeschool Athletic Association |
| CIAA | Cayman Islands Athletic Association |
| CIAA | Central Intercollegiate Athletic Association |
| CIAA | Central Intercollegiate Athletics Association |
| CIAA | Central Intermediate Athletic Association |
| CIAC | Carolinas Intercollegiate Athletic Conference |
| CIAC | Central Intercollegiate Athletic Conference |
| CIAC | Connecticut Interscholastic Athletic Conference |
| CIAU | Canadian Interuniversity Athletics Union |
| CIAW | Commission on Intercollegiate Athletics for Women |
| CISAA | Conference of Independent Schools Athletics Association |
| CISAC | Connecticut Independent School Athletic Conference |
| CMAA | Canadian Masters Athletic Association |
| CMAC | Central Michigan Athletic Conference |
| CMAC | Central Missouri Athletics Circuit |
| CMYA | Central Mississippi Youth Athletics |
| CNAA | Cardinal Newman Athletic Association |
| CNAA | Central Nassau Athletic Association |
| COAC | Central Oklahoma Athletic Conference |