| Abbreviation | Definition |
|---|---|
| RDSU | Russian Dance Sport Union |
| RDTU | Romanian Democratic Turkish Union |
| RDU | Road Diggers Union |
| REOU | Radio and Electronic Officers' Union |
| RESU | Renewable Energy Student Union |
| RFAA | Russian Female Art Association |
| RFU | Retained Firefighters Union |
| RFU | Retained Firefighters' Union |
| RFU | Russian Football Union |
| RG | Renegotiation Gains |
| RGU | Russell Gaelic Union |
| RGU | Russian Grain Union |
| RILU | Red International of Labour Unions |
| RLCA | Rural Letter Carrier Association |
| RMCU | Rocky Mountain Credit Union |
| RMIU | Railway Mazdoor Ittehad Union |
| RMN | Reunion des Musées Nationaux |
| RMT | National Union of Rail, Maritime, and Transport Workers |
| ROPE | Reunion of Professional Entertainers |
| RPEA | Retired Public Employees Association |