| Acronym | Definition |
|---|
| ISI | Inter-Services Intelligence (Pakistan) |
| ISI | Institute for Scientific Information |
| ISI | International Statistical Institute |
| ISI | Information Sciences Institute (at USC) |
| ISI | Intelligence and Security Informatics (Conference) |
| ISI | Inter-Symbol Interference (SONET) |
| ISI | Ice Skating Institute (Dallas, Texas) |
| ISI | Islamic State of Iraq (est. 2006) |
| ISI | Indian Statistical Institute |
| ISI | International Students, Inc. |
| ISI | Interstimulus Interval |
| ISI | Inter Service Intelligence (Pakistan) |
| ISI | Intracytoplasmic Sperm Injection |
| ISI | Interspike Interval |
| ISI | Import Substitution Industrialization |
| ISI | In Service Inspection(s) |
| ISI | Insulin Sensitivity Index |
| ISI | Fraunhofer Institut für Systemtechnik und Innovationsforschung (Germany) |
| ISI | Integrated Services Internet (IETF) |
| ISI | Integral Systems Inc. |
| ISI | Iron and Steel Institute |
| ISI | Indian Social Institute (New Delhi, India) |
| ISI | Information Security Institute (John Hopkins University) |
| ISI | Information Society Initiative |
| ISI | Institut Supérieur d'Informatique (Montréal) |
| ISI | Information Systems Integration |
| ISI | International Systems Institute |
| ISI | Intelligent Solutions, Inc. |
| ISI | Innovative Solutions International |
| ISI | Inter State Intelligence |
| ISI | Information Sharing Initiative (US Federal Bureau of Investigation) |
| ISI | Internally Specified Index |
| ISI | Inspection Speciale des Impots (Belgian) |
| ISI | Integrated Sourcing Initiative |
| ISI | Intelligent Serial Interface |
| ISI | Information Systems & Infrastructure |
| ISI | Information Spectrum, Inc. |
| ISI | Indian Standards Institute |
| ISI | Information Systems Inventory (US EPA) |
| ISI | International Sedimentation Initiative |
| ISI | Ingénierie des Systèmes d'Informations (French) |
| ISI | In Span Interconnect |
| ISI | Industrial Safety Integration |
| ISI | Ice Skating International |
| ISI | In School Isolation |
| ISI | Industry Support Interface |
| ISI | International Students Institute (Japan) |
| ISI | International School Ibadan (Nigeria) |
| ISI | Indigenous Survival International (Canada) |
| ISI | Information Services Interface |
| ISI | Integrated Storage Investigations |
| ISI | International Sale Indicator (airlines) |
| ISI | Interim Support Items |
| ISI | Information Sharing Infrastructure |
| ISI | Independent Solutions Inc. |
| ISI | Inquiry Scan Interval |
| ISI | Instrument/Spacecraft Interface |
| ISI | Industrial Safety Instructions |
| ISI | Information System Instrument |
| ISI | Initiation aux Sciences Informatiques |
| ISI | Inlet Spray Intercooling (gas turbine engines) |
| ISI | Industrial Steel Inc. (various locations) |
| ISI | Invisible Streams Incorporated |
| ISI | Inter-Service Institution (Indian Armed Forces) |
| ISI | Internal Special Investigations Office |
| ISI | International Systems Integration |
| ISI | Integrated Services Infrastructure |
| ISI | Integrated Serial Infrared |
| ISI | International Synergy Institute (Baltimore, MD) |
| ISI | Initial Stockage Items |
| ISI | Initial Support Increment |
| ISI | Imagesolutions, Inc. |
| ISI | Inspection Services, Inc. (various locations) |
| ISI | Insurance Services, Inc. (various locations) |
| ISI | Iron Sharpens Iron (religious gaming clan) |
| ISI | Interactive Software, Inc. (Dallas, TX) |
| ISI | Intuitive Surgical, Inc. (various locations) |
| ISI | Institute for School Improvement (Missouri State University) |
| ISI | International Standard Industrial (UN) |