| Abbreviation | Definition |
|---|---|
| IRI | International Rhumart Institute |
| IRIC | Islamic Research and Information Center |
| IRM | Institute of Risk Management |
| IRN | International Rivers Network |
| IRPS | Institute of Reconstructive Plastic Surgery |
| IRRC | Iowa Reading Research Center |
| IRRI | International Rice Research Institute |
| IRSA | Immigration and Refugee Services of America |
| IRSA | International RadioSurgery Association |
| IRSA | International Rett Syndrome Association |
| IRVA | International Remote Viewing Association |
| IRW | Islamic Relief Worldwide |
| IRWI | International Research Watch International |
| ISAP | Indian Society for Agribusiness Professionals |
| ISAR | Infobase of State Activities and Research |
| ISBA | International Society for Bayesian Analysis |
| ISBD | International Society for Behcet's Disease |
| ISBD | International Society of Bipolar Disorders |
| ISBE | I Sing the Body Electric Coalition |
| ISBE | International Society for Behavioural Ecology |