| Abbreviation | Definition |
|---|---|
| RHS | Red Hat Society |
| RHS | Romanian Horticultural Society |
| RHS | Royal Historical Society |
| RHS | Royal Horticultural Society |
| RHSA | Royal Humane Society of Australasia |
| RHSC | Royal Heraldry Society of Canada |
| RHSI | Royal Horticultural Society of Ireland |
| RIA | Acadamh Ríoga na hÉireann |
| RIA | Acadamh Roga na hireann |
| RIA | Robotic Industries Association |
| RIA | Royal Irish Academy |
| RIAI | Royal Institute of Architects of Ireland |
| RIAI | Royal Institute of the Architects of Ireland |
| RIC | Royal Institution of Cornwall |
| RICHES | Renewal Innovation and Change Heritage and European Society |
| RIDS | Rural Indian Development Society |
| RIHS | Rhode Island Historical Society |
| RILEM | International Union of Testing and Research Laboratories for Materials and Structures |
| RILEM | Réunion Internationale des Laboratoires d'Essais et de Recherches sur les Matériaux et les Constructions |
| RILEM | Runion Internationale des Laboratoires d'Essais et de Recherches sur les Matriaux et les Constructions |