| Abbreviation | Definition |
|---|---|
| ITSF | Indonesia Toray Science Foundation |
| ITSF | International Therapeutic Solidarity Fund |
| ITSO | Integrated Transport Smartcard Organisation |
| IUATLD | International Union Against Tuberculosis and Lung Disease |
| IUBF | International United Black Fund |
| IUBFI | International United Black Fund, Inc. |
| IUCA | Indo US Cultural Association |
| IUCN | International Union for Conservation of Nature and Natural Resources |
| IUFRO | International Union of Forest Research Organizations |
| IUGM | International Union of Gospel Missions |
| IVDA | Inter Varsity Dance Association |
| IVDK | Internationaler Verband der deutschen Kultur(in German) International Association of German Culture |
| IVP | International Volunteer Program |
| IVU | International Vegetarian Union |
| IWA | Institute of Welsh Affairs |
| IWB | International Whistle Blowers |
| IWBA | International Wound Ballistics Association |
| IWC | International Wildlife Conservancy |
| IWCA | International Wildfowl Carvers Association |
| IWFA | International Women's Fishing Association |