| Abbreviation | Description |
| IFAD | International Fund for Agricultural Development |
| IFC | International Finance Corporation |
| IFCTU | International Federation of Christian Trade Unions |
| IFRCS | International Federation of Red Cross and Red Crescent Societies |
| IGAD | Inter-Governmental Authority on Development |
| IGADD | Inter-Governmental Authority on Drought and Development |
| IHO | International Hydrographic Organization |
| IIB | International Investment Bank |
| ILO | International Labor Organization |
| IMF | International Monetary Fund |
| IMO | International Maritime Organization |
| Inmarsat | International Maritime Satellite Organization |
| InOC | Indian Ocean Commission |
| INSTRAW | International Research and Training Institute for the Advancement of Women |
| Intelsat | International Telecommunications Satellite Organization |
| Interpol | International Criminal Police Organization |
| Intersputnik | International Organization of Space Communications |
| IOC | International Olympic Committee |
| IOM | International Organization for Migration |
| IPU | Inter-parliamentary Union |
| ISO | International Organization for Standardization |
| ISP | Internet Service Provider |
| ITU | International Telecommunication Union |
| ITUC | International Trade Union Confederation (the successor to ICFTU (International Confederation of Free Trade Unions) and the WCL (World Confederation of Labor) |
| kHz | kilohertz |
| km | kilometer |
| kW | kilowatt |
| kWh | kilowatt-hour |
| LAES | Latin American Economic System |
| LAIA | Latin American Integration Association |