| Abbreviation | Definition |
|---|---|
| SSBU | Scottish Schools of Badminton Union |
| SSCU | Seven Seventeen Credit Union |
| SSCU | Social Security Credit Union |
| SSCU | Southern Star Credit Union |
| SSDSEU | Solomon Schechter Day School of Essex and Union |
| SSFCU | Suncoast Schools Federal Credit Union |
| SSU | Satellite Student Union |
| STA | Stage Techies Association |
| STF | Saskatchewan Teachers' Federation (Canada) |
| STFU | Southern Tenant Farmers Union |
| STK | Soluz Trudouogo Krest'ianstva (Russian - Union of Working Peasantry) |
| STOL | Sindicato de Trabajadores del Organismo Legislativo (Guatemala workers union) |
| STUC | Samoa Trade Union Congress |
| STUC | Samoa Trades Union Congress |
| STUC | Scottish Trades Union Congress |
| SU | Skinners Union |
| SU | Students Union |
| SUA | Student Union Assembly |
| SUA | Student Unions and Activities |
| SUAB | Student Union Activities Board |