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)

I – (s) Iodine – One (in Roman numerals)

I0–9
I2WD or I2WD – (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
IACREOT – (i) International Association of Clerks, Recorders, Election Officials, and Treasurers
IAD – (i) Ion Assisted Deposition
IADS – (i) Integrated Air Defence System
IAEA – (i) International Atomic Energy Agency
IAF – {i} Industrial Areas Foundation
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
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
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
IGFA – International Game Fish Association
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 [1]
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 – (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
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)
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 [2]
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)
IXT – (s) IntraText digital library; IntraText lexical hypertext

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)


== References ==