| Abbreviation | Definition |
|---|---|
| COGO | COmmunist in Government Groups |
| COI | Coordinator Of Information |
| COIN | COunter-INsurgency |
| COINTELPRO | COunter-INTELligence PROgram |
| COMFUG | COMmunist FUGitive |
| COMM-FBI | Files and COMMunication Division of the Federal Bureau of Investigation |
| COMPIC | COMmunist PICture album |
| COMPROS | Communist Party United States of America, PROSecution |
| CONUS | CONtinental United States |
| COSHH | Control of Substances Hazardous to Health Regulations of 2002 |
| CPC | Communist Pro-Chinese |
| CPDAI | Communist Party Domestic Administration Issue |
| CPIR | Communist Party International Relations |
| CPIU | Child Protection Investigation Unit |
| CPUSA | Communist Party United States of America |
| CRB | Criminal Records Bureau |
| CRCPO | Clandestine Radio Communications Potential Operator |
| CRITIC | CRITical Intelligence Communication |
| CRS | Can't Remember Squat |
| CRS | Central Records System |