| Abbreviation | Definition |
|---|---|
| SFWU | Seychelles Federation of Workers Unions |
| SFWU | Seychelles Federation of Workers' Unions |
| SHU | Santa Hat Union |
| SICA | Sindicato Independient de Colectivos Aeronáuticos |
| SICTU | Solomon Islands Council of Trade Unions |
| SILP | Sindacato Italiano Lavoratori Polizia (Italian: Italian Police Workers' Union) |
| SILU | Sugar Industry Labourers Union |
| SIMA | South Indian Millowners' Association |
| SINAP | Sindicato Nacional dos Papeleiros |
| SIPTU | Services Industrial Professional and Technical Union |
| SKDU | Syrian Kurdish Democratic Union |
| SKU | Super Kinies United |
| SLC | Standing Labor Committee |
| SLCTU | Sierra Leone Confederation of Trade Unions |
| SLCU | Scottish League Of Credit Unions |
| SLCU | Sierra Leone Central Union |
| SLCU | Soo Line Credit Union |
| SLCU | Southern Lakes Credit Union |
| SLCU | Spanish Lookout Credit Union |
| SLEMA | Sri Lanka Energy Managers Association |