| Abbreviation | Definition |
|---|---|
| IAGA | International Association of Geomagnetism and Aeronomy |
| IAGLR | International Association for Great Lakes Research |
| IAHS | International Association of Hydrological Sciences |
| IAI | Inter- American Institute for Global Change Research |
| IAMAP | International Association of Meteorology and Atmospheric Physics |
| IAMSLIC | International Association of Aquatic and Marine Science Libraries & Information Centers |
| iAOOS | Integrated Arctic Ocean Observing System |
| IAPG | Interagency Arctic Policy Group |
| IAPO | International Association for Physical Oceanography |
| IAPSO | International Association for the Physical Sciences of the Ocean |
| IARC | International Arctic Research Center |
| IARCC | Interagency Arctic Research Coordination Committee |
| IARCC | Inter-agency Arctic Research Coordination Committee |
| IASAP | International Arctic Seas Assessment Project |
| IASC | International Arctic Service Committee |
| IASPEI | International Association of Seismology and Physics of the Earth's Interior |
| IATTC | Inter-American Tropical Tuna Commission |
| IBC | International Bathymetric Chart |
| IBCCA | International Bathymetric Chart of the Caribbean Sea and the Gulf of Mexico |
| IBCEA | International Bathymetric Chart of the Central Eastern Atlantic |