Trade unions
C
| Full Name | Short Name | Notes |
|---|---|---|
| Card Setting Machine Tenters Society | CSMTS | |
| Ceramic and Allied Trades Union | CATU | |
| Chainmakers and Strikers' Association | CSA | |
| Chartered Society of Physiotherapy | CSP | |
| Chemical Workers' Union | ChWU | |
| Civil and Public Services Association | CSPA | |
| Civil Service | Civil Service | |
| Civil Service Clerical Association | CSCA | |
| Clerical and Administrative Workers' Union | CAWU | |
| Commercial Travellers' Association of Great Britain | CTAGB | a.k.a. United Kingdom Commercial Travellers' Association |
| Communication Workers Union | CWU | |
| Community | Community | |
| Community and District Nursing Association | CDNA | |
| Community and Youth Workers' Union | CYWU | |
| Confederation of Engineering and Shipbuilding Trades | CEST | |
| Confederation of Health Service Employees | COHSE | |
| Connect | Connect | |
| Conservative Trade Union Association | Cons TU | |
| Constructional Engineering Union | CEU | |
| Co-operative | Co-op |