IS
- is – (s) Icelandic language (ISO 639-1 code)
- IS
- (s) Iceland (ISO 3166 digram)
- Israel (FIPS 10-4 country code)
- ISA
- (i) Individual Savings Account
- Industry Standard Architecture
- Instruction Set Architecture
- International Seabed Authority
- ISAAA – (i) International Service for the Acquisition of Agri-biotech Applications
- ISAF
- (a) International Sailing Federation
- International Security Assistance Force
- ISAR – (a) Inverse SAR (Synthetic Aperture Radar)
- ISB – (i) Intermediate Staging Base
- ISBN – (i) International Standard Book Number (ISO 2108)
- ISCCP – (i) International Satellite Cloud Climatology Project
- ISCII – (a) Indian Standard Code for Information Interchange
- ISDN – Integrated Services Digital Network
- ISEF – (a) Intel International Science and Engineering Fair
- ISEN – (i) Internet Search Environment Number
- ISF – (i) Internal Security Force
- ISI
- Indian Standards Institute, former name of the Bureau of Indian Standards
- Inter-Services Intelligence (Pakistan)
- Islamic State of Iraq, an umbrella organization for several Iraqi insurgent groups
- ISIS – (i/a) Institute for Science and International Security
- ISK – (s) Icelandic krona (ISO 4217 currency code)
- isl – (s) Icelandic language (ISO 639-2 code)
- ISL – (s) Iceland (ISO 3166 trigram)
- ISLN – (i) International Standard Lawyer Number (used initially by LexisNexis Martindale-Hubbell)
- ISM
- (i) Industrial, scientific or medical
- (p) Interstellar medium
- ISMB – (i) International Society of Matrix Biologists
- ISMC – (i) Intelligent Sounding Meaningless Conversation
- ISO
- (i) In Search Of
- (s) International Organization for Standardization (from the Greek ίσος, isos, meaning "equal")
- ISOGP – (i) Indian Society of Orthodontics for General Practitioners
- ISP
- (i) International Standardized Profile
- Internet Service Provider
- Information Systems Professional
- ISPE – (a/i) International Society for Pharmacoepidemiology
- ISR
- (i) Intelligence, Surveillance and Reconnaissance
- (s) Israel (ISO 3166 trigram)
- ISRO – (i) Indian Space Research Organisation
- ISS
- (i) International Shorebird Survey (North America)
- International Space Station
- ISSCR – (i) International Society for Stem Cell Research
- ISSN – (i) International standard serial number (ISO 3297)
- IST
- (i) Information System Technology
- UCF Institute for Simulation and Training
- ISTAR – (i) Intelligence, Surveillance, Target Acquisition, and Reconnaissance
- ISTC – (i) Institute of Scientific and Technical Communications (UK)
- ISTS – (i) Intel Science Talent Search
- ISU
- (i) Integrated Sight Unit
- International Skating Union
Read more about this topic: List Of Acronyms And Initialisms: I