# List of acronyms: I

This list contains acronyms, initialisms, and pseudo-blends that begin with the letter I.
For the purposes of this list:
* acronym = an abbreviation pronounced as if it were a word, e.g., SARS = severe acute respiratory syndrome, pronounced to rhyme with cars
* initialism = an abbreviation pronounced wholly or partly using the names of its constituent letters, e.g., CD = compact disc, pronounced cee dee
* pseudo-blend = an abbreviation whose extra or omitted letters mean that it cannot stand as a true acronym, initialism, or portmanteau (a word formed by combining two or more words).
    (a) = acronym, e.g.: SARS – (a) severe acute respiratory syndrome
    (i) = initialism, e.g.: CD – (i) compact disc
    (p) = pseudo-blend, e.g.: UNIFEM – (p) United Nations Development Fund for Women
    (s) = symbol (none of the above, representing and pronounced as something else; for example: MHz – megahertz)
Some terms are spoken as either acronym or initialism, e.g., VoIP, pronounced both as voyp and V-O-I-P.
(Main list of acronyms)

## Contents

* Top
* I0–9 IA IB IC ID IE IF IG IH II IJ IK IL IM IN IO IP IQ IR IS IT IU IV IW IX IY IZ
* I – (s) Iodine – One (in Roman numerals)

## I0–9

* I2WD or I$^2$WD – (i) U.S. Intelligence and Information Warfare Directorate (CERDEC)

## IA

* ia – (s) Interlingua language (ISO 639-1 code)
* IA – (s) Iowa (postal symbol)
* IAAF – (i) International Association of Athletics Federations ("International Amateur Athletics Federation" from 1912 to 2001; renamed "World Athletics" in 2019)
* IAAL – (i) I Am A Lawyer
* IAAS - (p) Infrastructure-as-a-Service
* IAB –
** (i) International Association for Biologicals
** IATA code of McConnell Air Force Base
* IACREOT – (i) International Association of Clerks, Recorders, Election Officials, and Treasurers
* IAD –
** (i) Ion Assisted Deposition
** IATA code for Washington Dulles International Airport
* IADS – (i) Integrated Air Defence System
* IAE - (i) International Aero Engines (aircraft engine joint venture)
* IAEA – (i) International Atomic Energy Agency
* IAF
** {i} Industrial Areas Foundation
** (i) Israeli Air Force
* IAFG – (i) Information Assurance Focus Group
* IAI –
** (i) International African Institute
** Israel Aircraft Industries
* IANA – (i) Internet Assigned Numbers Authority
* IANAL – (i) I Am Not A Lawyer
* IAPD
** International Associates of Paediatric(sic) Dentistry
** (i) Investment Adviser Public Disclosure
** iShares Asia Pacific Dividend
* IAQ – (i) Indoor air quality – Infrequently Asked Questions
* IAS – (i) Image Assessment System
* IASIP – (i) It's Always Sunny in Philadelphia
* IATA – (a/i) International Air Transport Association
* IATF – International Automotive Task Force
* IATSE – International Alliance of Theatrical Stage Employees
* IAU – (i) International Association of Universities – International Astronomical Union
* IAUC – (i) International Astronomical Union Circular
* IAW – (i) In Accordance With

## IB

* IB – (i) International Baccalaureate
* IBA – (i) Important Bird Area
* IBD – (i) Inflammatory Bowel Disease
* IBDM – (i) Information Based Decision Making
* IBDS – (i) Integrated Biological Detection System – International Business Development Specialist
* IBF - International Boxing Federation
* IBGe – (i) Isobutylgermane
* IBGE – (i) Instituto Brasileiro de Geografia e Estatística (Portuguese, "Brazilian Institute of Geography and Statistics")
* IBHOF - International Boxing Hall of Fame
* IBM – (i) International Business Machines
* ibo – (s) Igbo language (ISO 639-2 code)
* IBRD – (i) International Bank for Reconstruction and Development (part of the World Bank)
* IBS – (i) Irritable Bowel Syndrome

## IC

* IC
** (s) Ice Crystals (METAR Code)
** Iceland (FIPS 10-4 country code)
** (i) Integrated Circuit - [inner circle]
* ICANN – (a) Internet Corporation for Assigned Names and Numbers
* ICAO – (i) International Civil Aviation Organization
* ICBM – (i) Intercontinental Ballistic Missile
* ICBM – I see (phonetically "c") BatMan
* ICBN – (i) International Code of Botanical Nomenclature
* ICC
** (i) Integrated Command and Control
** International Criminal Court
** International Cricket Council
** Interstate Commerce Commission
** International Chamber of Commerce
* ICD
** (i) Implantable Cardioverter-Defibrillator
** Initial Capabilities Document
** International Classification of Diseases
* ICE
** (i/a) (U.S.) Immigration and Customs Enforcement
** In case of emergency
** Internal Combustion Engine (Vehicles)
* ICES – (a/i) International Council for the Exploration of the Sea
* ICF – (i) Intelligent Community Forum
* ICHTHYS – (a) Iesous Christos, Theou Yios, Soter (Greek, "Jesus Christ, Son of God, Savior")
* ICM
** (i) Improved Conventional Munition
** Integrated Collection Management
** International Congress of Mathematicians
** Iraq Campaign Medal
* ICMP – (i) Internet Control Message Protocol
* ICNAF – (i) International Commission for the Northwest Atlantic Fisheries (became NAFO in 1978)
* ICNI – (i) Integrated Communication, Navigation, and Identification
* ICO – (i) Intermediate Circular Orbit
* ICP
** (i) Inductively coupled plasma
** Insane Clown Posse
* ICPE – (a/i) International Conference on Pharmacoepidemiology, the annual conference of the International Society for Pharmacoepidemiology
* ICRAF – (i) International Centre for Research in Agroforestry (a.k.a. World Agroforestry Centre since 2002)
* ICRISAT – (i/a) International Crops Research Institute for the Semi-Arid Tropics
* ICRL – (i) Individual Component Repair List
* ICRS – (i) International Celestial Reference System
* ICS
** (i) In-Country Support
** Intelligence and Communications Systems
** Interim Contractor Support
* ICSI – (p) Intracytoplasmic Sperm Injection
* ICT – (i) Information and communication technologies
* ICTH – (i) Island Closest to Heaven/Hell Final Fantasy VIII
* ICV – (i) Infantry Carrier Vehicle
* ICW
** (i) In Co-ordination With
** Indonesia Corruption Watch
** Infectious and Chemotherapeutic Waste
** Insulating Concrete Wall
** Integral Crystalline Waterproofing
** (p) Interactive Courseware
** (i) International Championship Wrestling (defunct US professional wrestling promotion)
* ICYMI – (i) In Case You Missed It
* ICZN
** (i) International Code of Zoological Nomenclature
** International Commission on Zoological Nomenclature

## ID

* id – (s) Indonesian language (ISO 639-1 code)
* ID
** (s) Idaho (postal symbol)
** (p) Identity
** (s) Indonesia (FIPS 10-4 country code; ISO 3166 digram)
** (i) Infantry Division
** Intelligent Design
* ID10T Error – (i) Idiot User Error (IT help desk inside joke)
* IDA
** (i) U.S. Institute for Defense Analyses
** International Development Association (part of the World Bank
* IDC – (i)
** International Data Corporation
** "I Don't Care"
* IDDI – (i) I don't do initialisms (see irony)
* IDE
** (i) Integrated Development Environment
** Integrated Drive Electronics
* IDeA – (a) Improvement and Development Agency, the former name of Local Government Improvement and Development in the United Kingdom
* IDEA
** (a) Individuals with Disabilities Education Act (U.S.)
** International Data Encryption Algorithm
** International Design Excellence Awards
* IDF
** (i) Israel Defense Forces
** Intel Development Forum
** International Dairy Federation
* IDGAF – (i) I don't give a f**k
* IDK – (i) I don't know
* IDKIBTI – I don't know, I'm black, that's it
* IDL – (i) Interface Definition Language
* IDN – (s) Indonesia (ISO 3166 trigram)
* ido – (s) Ido language (ISO 639-2 code)
* IDR – (s) Indonesian rupiah (ISO 4217 currency code)
* IDTS – (i) I don't think so

## IE

* i.e. – (i) id est (Latin, roughly "that is")
* ie – (s) Interlingue language (ISO 639-1 code)
* IE – (i) Indo-European languages – Internet Explorer – (s) Ireland (ISO 3166 digram) – Iced Earth
* IEA – (i) International Energy Agency
* IEC – (i) International Electrotechnical Commission
* IED – (i) Improvised Explosive Device
* IEEE – (p) Institute of Electrical and Electronics Engineers ("I triple-E")
* IELTS – (a) International English Language Testing System
* IER – (i) Information Exchange Requirement
* IET – (i) Institution of Engineering and Technology
* IET – (ii) Initial Entry Training
* IETF – (i) Internet Engineering Task Force
* IEW – (i) Intelligence and Electronic Warfare

## IF

* IFAB – (i) International Football Association Board
* IFAH – (i) International Federation for Animal Health
* IFAP – (i) International Federation of Agricultural Producers, (i) International Fashion Academy Pakistan
* IFC – (i) International Finance Corporation (part of the World Bank) – (a) Independent Film Channel
* IFF – (i) Identification, Friend or Foe – Individually Fresh Frozen – International Flavors and Fragrances
* IFFN – (i) Identification, Friend, Foe, or Neutral
* IFO – (i) Identified Flying Object (see also UFO)
* IFOR – (p) UN Implementation Force – (i) Institute for Operations Research – International Fellowship of Reconciliation
* IFOV – (i) Instantaneous Field of View
* IFPI – (i) International Federation of Phonographic Industries
* IFR – (i) Instrument Flight Rules
* IFRB – (i) International Frequency Registration Board
* IFV – (i) Infantry Fighting Vehicle

## IG

* ig – (s) Igbo language (ISO 639-1 code)
* IG –
** (i) Inspector General
** Instagram
* IGFA – International Game Fish Association
* IGM - IATA code for Kingman Airport
* IGNOU – (a) Indira Gandhi National Open University
* IGS – (i) International Ground Station
* IGY – (i) Israeli Gay Youth – International Geophysical Year

## IH

* IHÉS – (i) Institut des Hautes Études Scientifiques (French, Institute of Advanced Scientific Studies)
* IHH – (i) Idiopathic Hypogonadotropic Hypogonadism
* IHO – (i/a) International Hydrographic Organization
* IHOP – (i/a) International House of Pancakes, the original name of this American restaurant chain ("EYE-hop")
* IHR – (i) Institute for Historical Review
* IHSI – Institutum Historicum Societatis Iesu (Jesuit Historical Institute)

## II

* ii – (s) Sichuan Yi language (ISO 639-1 code)
* II – (s) Two (in Roman numerals)
* IICA – (i) Inter-American Institute for Cooperation on Agriculture
* IIE – (i) Innovative Interstellar Explorer
* iii – (s) Sichuan Yi language (ISO 639-2 code)
* III – (s) Three (in Roman numerals)
* IIMSS – If I May Say So
* IIRC – If I Remember Correctly, If I Recall Correctly
* IISS – (i) International Institute for Strategic Studies
* IIT – (i) Illinois Institute of Technology – Indian Institutes of Technology – Indiana Institute of Technology
* IITM – (i) Image Institute of Technology & Management – Indian Institute of Technology Madras – Indian Institute of Tropical Meteorology
* I/ITSEC – (a) Interservice/Industry Training, Simulation and Education Conference ("eye-it-sec" or "it-sec")

## IJ

* IJN – (i) Imperial Japanese Navy (World War II)
* IJWP – (i) Interim Joint Warfare Publication

## IK

* ik – (s) Inupiaq language (ISO 639-1 code)
* IKEA – (a) Ingvar Kamprad (the company's founder), Elmtaryd (the farm where he was born and raised), Agunnaryd (a village and parish near the farm)
* iku – (s) (s) Inuktitut language (ISO 639-2 code)

## IM

* IM
** (s) Isle of Man (FIPS 10-4 territory code)
** (i) Instant Message (Internet speech)
* IMA
** (i) Intermediate Maintenance Activity
** Institute of Mathematics and Applications
* IMBD – (i) International Migratory Bird Day
* IMDb – Internet Movie Database
* IME - (i) In My Experience
* IMF
** (i) id music file/id's music format (audio file format)
** Impossible Missions Force, the protagonist organization in the Mission: Impossible media franchise
** International Monetary Fund (the most common use for the initialism)
* IMHO – (i) In My Humble/Honest Opinion, cf. IMO
* IMIST AMBO – used to facilitate an informed clinical handover between paramedics, emergency department staff or other healthcare similar to SBAR: Identification, Method of Injury, Index of concern, Signs, Treatment, Allergies, Medication, Background, and Other
* IML – (i) International Mister Leather
* IMLAST – (i) International Movement for Leisure Activities in Science and Technology – see MILSET
* IMNM - (i) - Immune-mediated necrotizing myopathy a rare, but serious ADR of statins
* IMNSHO – (i) In My Not So Humble Opinion
* IMO (in my opinion) – (i) In My Opinion, also "imo", cf. IMHO
* IMPAC – (a) International Merchant Purchase Authorization Card
* IMPACT – (a) International Medical Products Anti-Counterfeiting Taskforce
* IMPATT – (p) IMPact Avalanche Transit Time diode
* IMPT – (i) Institute of Maxillofacial Prosthetists and Technologists
* IMR – (i) Inzhenernaya Mashina Razgrazhdeniya (Russian Инженерные Машины Разграждения, "Engineer Vehicle Obstacle-Clearing") †
* IMRI
** (i) Industrial Membrane Research Institute
** Information Management Research Institute
** Institut pour le management de la recherche et de l'innovation (French, "Institute for the Management of Research and Innovation")
** International Market Research Information
** Intraoperative Magnetic Resonance Imaging
* IMRO
** Internal Macedonian Revolutionary Organization
** Irish Music Rights Organisation
* IMRL – (i) Individual Material Readiness List
* IMS
** (i) Information Management System
** International Meat Secretariat
** Ion Mobility Spectrometer
* IMSA
** (i) Illinois Mathematics and Science Academy
** International Mind Sports Association
** International Motor Sports Association
* IMsL – (a) International Ms. Leather
* IMT – (i) Integrated Management Tool
* IMU – (i) International Mathematical Union

## IN

* In – (s) Indium
* IN – (s) India (FIPS 10-4 country code; ISO 3166 digram) – Indiana (postal symbol) – Infantry
* ina – (s) Interlingua language (ISO 639-2 code)
* INA – (p) Immigration and Nationality Act
* INAS – (a) International Near-Earth Asteroid Survey
* INC – (i) Indian National Congress, one of the national political parties in India
** (i) Iglesia ni Cristo (Filipino, "Church of Christ")
** Indian National Congress
** International Network of Crackers
** Iraqi National Congress
* INCITS – (p) InterNational Committee for Information Technology Standards
* ind – (s) Indonesian language (ISO 639-2 code)
* IND – (s) India (ISO 3166 trigram)
* inet – (a) the Internet
* INDIGO – (p) (U.S.) INtelligence DIvision Gaming Operation
* INFORMS – (a) (U.S.) Institute for Operations Research and the Management Sciences
* INFOSEC – (p) Information Security
* INLA – (i) Irish National Liberation Army
* INMARSAT – (p) International Maritime Satellite organization
* INR – (s) Indian rupee (ISO 4217 currency code)
* INRI – (a/i) Iesus Nazarenus Rex Iudæorum (Latin, "Jesus of Nazareth, King of the Jews")
* INRIA – (p) Institut national de recherche en informatique et en automatique
* INS – (i) Immigration and Naturalization Service
* InSAR – (p) Interferometric synthetic aperture radar
* INST – (p) Information Standards and Technology
* in trans. – (p) in transitu (Latin, "in transit")
* INTSUM – (p) Intelligence Summary
* INTERFET – (p) International Force for East Timor

## IO

* io – (s) Ido language (ISO 639-1 code)
* IO – (s) British Indian Ocean Territory (ISO 3166 digram; FIPS 10-4 territory code)
* IOC
** (i) Initial Operational Capability
** Intergovernmental Oceanic Commission
** International Olympic Committee
** International Ornithological Congress
* IOG (formerly IOHK) – Input Output Global. Redirected to Charles Hoskinson
* IOHK – Input Output Hong Kong. Redirected to Charles Hoskinson
* IOLTA – (a) Interest on Lawyer Trust Accounts (charitable funding mechanism, especially for legal aid)
* IOM
** (i) Iowa, Ohio, Michigan (soybean origin)
** Institute of Medicine
** International Organisation for Migration
** Isle of Man
* IONA – (i) Islands of the North Atlantic (alternate name for Great Britain, Ireland, the Isle of Man, and related islands)
* IoT - (i) Internet of Things
* IOT – (s) British Indian Ocean Territory (ISO 3166 trigram)
* IOT&E – (i) Initial Operational Test and Evaluation
* IOU – (p) "I Owe You" (Promissory note)

## IP

* IP –
** (s) Clipperton Island (FIPS 10-4 territory code)
** (i) Initial Point – Intellectual Property – Internet Protocol
* IPA – (i) India Pale Ale – International Phonetic Alphabet – Isopropyl alcohol
* IPB – (i) Intelligence Preparation of the Battlefield
* IPCC –
** (i) Intergovernmental Panel on Climate Change
** Independent Police Complaints Commission
* ipk – (s) Inupiaq language (ISO 639-2 code)
* IPL – (i) Inferior Parietal Lobule
* IPN – (i) Instytut Pamieci Narodowej (Polish, "Institute for National Memory")
* IPO – (i) Initial public offering
* IPR –
** (i) In Progress Review
** Intellectual Property Rights
** Intelligence Production Requirement
* IPT – (i) Integrated Product/Project Team
* IPTS – (i) Institute for Prospective Technological Studies
* IPTV – (p) Internet Protocol TeleVision
* IPW – (i) Interrogation of Prisoners of War

## IQ

* iq – (i) idem quod (Latin, "the same as")
* IQ –
** (i) Intelligence Quotient
** (s) Iraq (ISO 3166 digram)
* IQD – (s) Iraqi dinar (ISO 4217 currency code)

## IR

* Ir – (s) Iridium
* IR
** (i) Infrared
** Intelligence requirement (military)
** (s) Iran (FIPS 10-4 country code; ISO 3166 digram)
** Iran Air (IATA alpha code) see entry for more
* IRA
** (i) Individual retirement account
** (i) Irish Republican Army (any of several armed groups dedicated to Irish republicanism)
** Internet Research Agency (used in the Mueller report)
* IRAD – (a) Internal Research and Development
* IRAN - (I) Inspect and Repair As Necessary
* IRAS – (p) Infrared Astronomical Satellite
* IRB – (i) International Rugby Board, a former name of World Rugby
* IRBM – (i) Intermediate Range Ballistic Missile
* IRC
** (i) International Red Cross
** International reply coupon
** (i) Internet Relay Chat
* IREA
** (i) Intermountain Rural Electric Association
** (i) International Renewable Energy Alliance
** (p) Iranian Esperanto Association
** (i) Internet Radio Equality Act
* IRGC - (i) Islamic Revolutionary Guard Corps (branch of Iranian Armed Forces
* IRL
** (s) Ireland (ISO 3166 trigram)
** Industrial Research Limited
** Indy Racing League, former name of the motorsport governing body now known as INDYCAR
** (i) In real life
* IRM
** (i) Illinois Railway Museum
** Inzhenernaya Razvedyvatelnaya Mashina (Russian Инженерная Разведывательная Машина, "Engineer Reconnaissance Vehicle") †
* IRN – (s) Iran (ISO 3166 trigram)
* IRIAF - Islamic Republic of Iran Air Force
* IRINN - Islamic Republic of Iran News Network
* IRO – (i) International Refugee Organisation
* IRQ – (s) Iraq (ISO 3166 trigram)
* IRR – (s) Iranian rial (ISO 4217 currency code)
* IRS – (i) U.S. Internal Revenue Service
* IRSN – (i) Institut de radioprotection et de sûreté nucléaire (French, "Institute for Radiation Protection and Nuclear Safety")
* IRST – (i) Infra-red Search and Track

## 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
* ISIL – (i/a) Islamic State of Iraq and the Levant
* ISIS
** (i/a) Institute for Science and International Security
** Islamic State of Iraq and Syria
* 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)
** (i) International School Libraries Network (HQ in Singapore)
** (s) Isilon Systems, the NASDAQ symbol
* 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)
* ISTG – (i) I Swear To God
* ISTS – (i) Intel Science Talent Search
* ISU
** (i) Integrated Sight Unit
** International Skating Union

## IT

* it – (s) Italian language (ISO 639-1 code)
* IT
** (i) InferoTemporal (neurophysiology)
** Information Technology
** (s) Italy (FIPS 10-4 country code; ISO 3166 digram)
* ita – (s) Italian language (ISO 639-2 code)
* ITA – (s) Italy (ISO 3166 trigram)
* ITAG – (i) Inertial Terrain-Aided Guidance
* ITALY – (a) I'll Truly Always Love You
* ITAS – (i) Improved Target Acquisition Sight
* ITC
** (i) Incorporated Television Company (defunct British television production company)
** InferoTemporal Cortex (neurophysiology)
* ITCZ – (i/p) Intertropical Convergence Zone
* ITEC – (a) Information Technology Exposition & Conference
* ITEMS – (a) Interactive Tactical Environment Management System
* ITER – (a) International Thermonuclear Experimental Reactor
* ITF – (a) International Tennis Federation
* ITK – (a) In The Know
* ITN – (i) Independent Television News (British)
* ITS
** (i) Incompatible Time-sharing System
** Individual Training Standards
* ITT – (i) International Telephone and Telegraph (U.S.)
* ITTO – (i) International Tropical Timber Organization
* ITU
** (i) Intent-to-Use
** International Telecommunication Union (International Telegraph Union 1865–1932)

## IU

* iu – (s) (s) Inuktitut language (ISO 639-1 code)
* IUCN – (i) International Union for the Conservation of Nature and Natural Resources (World Conservation Union)
* IUD – (i) Intrauterine device (https://www.plannedparenthood.org/learn/birth-control/iud)
* IUI
** (i) Indiana University Indianapolis, to be established in 2024 upon the dissolution of Indiana University–Purdue University Indianapolis (IUPUI, below)
** Intrauterine insemination (http://americanpregnancy.org/infertility/intrauterine-insemination/)
* IUPAC – (a) International Union of Pure and Applied Chemistry (pronounced "eye-yoo-pac")
* IUPUI – (a) Indiana University–Purdue University Indianapolis
* IUSS
** (i) Integrated Undersea Surveillance System
** Integrated Unit Simulation System
** International Union of Soil Sciences

## IV

* IV – (s) Côte d'Ivoire (FIPS 10-4 country code; from Ivory Coast) – Four (in Roman numerals) – (i) IntraVenous (as in intravenous drip or intravenous therapy)
* IVD – (i) Internet Video Device, intra vas device
* Iveco – (p) Industrial Vehicles Corporation
* IVF – (i) In Vitro Fertilisation
* IVI – (i) Interchangeable Virtual Instrument
* IVIS – (i/a) Inter-Vehicle Information System
* IVL – (i) Inter-Visibility Line
* IVM – (i) In Vitro [Oocyte] Maturation
* IVO – (i) In Vicinity Of

## IW

* IW – (i) Impact Wrestling
* IW – (i) Information Warfare
* IWARS – (p) Infantry Warrior Simulation
* IWC – (i) International Whaling Commission
* IWT – (i) Illegal Wildlife Trade
* IWW – (i) Industrial Workers of the World

## IX

* IX – (s) Nine (in Roman numerals)

## IY

* IY – (s) Saudi–Iraqi neutral zone (FIPS 10-4 territory code; obsolete 1993)
* Iykyk (acronym) – (i) If You Know You Know

## IZ

* IZ – (s) Iraq (FIPS 10-4 country code)