| Acronym | Meaning |
| IFRTS | Internal-floating-roof Tanks |
| IFSD | In-Flight Shutdown |
| IFSEM | International Federation Of Societies For Electron Microscopy |
| IFT | Interfacial Tension |
| IFW | Image File Wrapper |
| IGA | Inert-gas Atomization |
| IGAC | International Global Atmospheric Chemistry |
| IGAIM | Individual Gages (for) Atoms In Molecules |
| IGARSS | International Geoscience And Remote Sensing Symposium |
| IGBP | International Geosphere Biosphere Programme |
| IGBT | Insulated Gate Bipolar Transistor |
| IGC | International Geological Congress |
| IGC | Intergranular Corrosion |
| IGC | Inverse Gas Chromatog. |
| IGCAR | Indira Gandhi Center Atomic Research |
| IGCC | Integrated Gasification Combined Cycles (electric Power Generation Technology) |
| IGCI | Industrial Gas Cleaning Institute |
| IGCP | International Geological Correlation Program |
| IGEFET | Interdigitated-gate-electrode Field-effect Transistor |
| IGES | Institute Of Global Environment And Society |
| IGF | Inert Gas Fusion |
| IGF | Insulin-like Growth Factor |
| IGF | Irreducible Green Function |
| IGFA | Inert Gas Fusion Analysis |
| IGFBP | Insulin-like Growth Factor-binding Proteins |
| IGFET | Insulated Gate Field Effect Transistor |
| IGGE | Institute Of Geophysical And Geochemical Exploration |
| IGHAT | Integrated-gasification Humid-air Turbine [cycle] |
| IGLO | Individual Gauge For Localized Orbital |
| IGOR | Interactive Generation Of Organic Reactions |
| IGOSS | Integrated Global Ocean Services System |
| IGP | Intergranular Penetration |
| IGPP | Institute Of Geophysics And Planetary Physics |
| IGS | Intergenic Spacer |
| IGSCC | Intergranular Stress Corrosion Cracking |
| IGT | Institute Of Gas Technology |
| IGT | Impaired Glucose Tolerance |
| IGT | Insulated-gate Transistor |
| IGWMC | International Ground Water Modeling Center |
| IGY | International Geophysical Year |
| IHC | Interim Hazard Classification |
| IHC | Intrinsic Coercivity |
| IHEA | Industrial Health Engineering Association |
| IHF | Inhomogeneous Hartree-Fock |
| IHF | Integration Host Factor |
| IHMM | Institute Of Hazardous Materials Management |
| IHO | International Hydrographic Association |
| IHP | Inositol Hexaphosphate |
| IHSI | Induction Heating Stress Improvement |
| IHSS | International Humic Substances Society |