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 – Irish Republican Army (see also List of organisations known as the Irish Republican Army for groups claiming descent from this organisation)
- IRAD – (a) Internal Research and Development
- IRAS – (p) Infrared Astronomical Satellite
- IRB – (i) International Rugby Board
- IRBM – (i) Intermediate Range Ballistic Missile
- IRC – (i) International Red Cross – International Reply Coupon – Internet Relay Chat
- IREA – (i) Intermountain Rural Electric Association
- IRL – (s) Ireland (ISO 3166 trigram) – Industrial Research Limited – Indy Racing League – 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
Read more about this topic: List Of Acronyms And Initialisms: I