| Abbreviation | Definition |
|---|---|
| ISSC | International Social Science Council |
| IT-95 | Information Technology 1995 |
| ITA | International Trade Administration |
| ITCZ | Intertropical Convergence Zone |
| ITIC | International Tsunami Information Center |
| ITL | International Towing Limited |
| ITMS | Interactive Tsunami Modeling System |
| ITOS | Improved TIROS Operational Satellite |
| ITPR | Infra-red Temperature Profile Radiometer |
| ITQ | Individual Transferable Quota |
| ITRIS | Integrated Tsunami Research and Information System |
| ITSU | International Coordination Group for the Tsunami Warning System in the Pacific |
| ITU | International Telecommunication Union |
| ITWS | Integrated Terminal Weather System |
| IUBS | International Union of Biological Sciences |
| IUCN | International Union for Conservation of Nature and Natural Resources |
| IUGG-TC | IUGG Tsunami Commission |
| IUH | Instantaneous Unit Hydrograph |
| IUM | Interocean Ugland Management Corporation |
| IUSS | Integrated Underwater Surveillance System |