| Ilkley Grammar School | Academic & Science |
| Ivanhoe Grammar School | Academic & Science |
| Islington Green School | Academic & Science |
| International Geosynthetics Society | Academic & Science |
| International Gentlemans Society | Academic & Science |
| International Glaciological Society | Academic & Science |
| החברה הגיאולוגית הישראלית | Academic & Science |
| International Grammar School | Academic & Science |
| Israel Geological Society | Academic & Science |
| Inner Gulf Shelf | Academic & Science |
| Indian Geotechnical Society | Associations & Organizations |
| Institute of General Semantics | Associations & Organizations |
| Irish Georgian Society | Associations & Organizations |
| Information Gateway Services | Business |
| Investor Group Services | Business |
| Information Global Service | Business |
| International Goldfields Limited... | Business |
| Insoluble Glue Substances | Chemistry |
| Ipswich Grammar School | Community |
| Integrated Gaming System | Computing |
| I Guess So | Computing |
| Independent Gaming Solutions | Computing |
| Inter Graphics Systems | Computing |
| Ibm Global Services | Computing |
| Interchange Group Separator | Computing |
| Interactive Geometry Software | Computing |
| Internet Go Server | Computing |
| 2D or 3D CAD model Initial Graphics Exchange Specification format | Computing |
| Institute of Geological Sciences | Earth Science |
| Image Systems Grayscale | File Type |
| Industrial Gateway Server | General |
| Idaho Geological Survey | General |
| Image Guided Systems | General |
| Iowa Geological Survey | General |
| Intelligent Glass Solutions | General |
| International Green Structures | General |
| Integrated Global Services | General |
| Indiana Geological Survey | General |
| Island Guardian Series | General |
| Integrated Gas System | General |
| Intelligent Global Solutions | General |
| Integrated Group Services | General |
| Intelligence Gathering Satellite | General |
| Indian Gospel Singers | General |
| Intelligent Guide System | General |
| Information Gathering Satellite | General |
| Instantaneous Gearchange System | General |
| Inter Genic Spacer | General |
| Informational Global Services | General |
| Iranian Gas Standards | General |
| Information Gathering Satellites | General |
| Infinite Game Shows | General |
| Ins Giant System | General |
| International Guitar Seminars | General |
| Impact Guidance System | General |
| Indoor Grow System | General |
| Inter-Generational Snapshot | General |
| International GNSS Service | General |
| Indian Government Service | Governmental |
| Institute of Graduate Studies | Governmental |
| International Graduates Scheme | Governmental |
| Institute of Governmental Studies | Governmental |
| Information Governance Solutions | Governmental |
| Institute for Graduate Studies | Governmental |
| Institute for Guided Studies | Governmental |
| International Gps Service | Governmental |
| Instrument Guidance System | Governmental |
| International GNSS (Global Navigation Satellite System) Service | Governmental |
| Institute for Global Studies | Governmental |
| International Guest Scholarships | International |
| International Genetic Standardization | International |
| International Gem Society | International |
| International Geoscience Services | International |
| International Glass Solutions | International |
| International Geosynthetic Society | International |
| International Grantmaking Symposium | International |
| International and Global Studies | International |
| International Global Studies | International |
| Imerslund-Gräsbeck Syndrome | Medical |
| Irritable Gripe Syndrome | Medical |
| Institute for Genome Sciences | Medical |
| Image-Guided Surgery | Medical |
| Inappropriate Gonadotropin Secretion | Medical |
| Information Governance Strategy | Medical |
| Instrument Guiding System | Military and Defence |
| Intermediate General Support | Military and Defence |
| iGATE Global Solutions Limited | NSE Company Symbol |
| Inertial Guidance System | Space Science |
| International Games System | Sports |
| Ingolstadt Manching Airport | Transport & Travel |