IR
- .ir
- Adobe ImageReady
- I Am Weasel
- IR Ishikawa Railway
- IRS (disambiguation)
- Iarnród Éireann
- Illinois Railway
- Image retention
- Imaginary number
- Imperial–royal
- Impulse response
- Incidence Rate
- Incidence rate (market research)
- Independent-Republican Party of Minnesota
- Indian Railways
- Indian Reserve
- Industrial relations
- Information ratio
- Information retrieval
- Information revolution
- Infrared
- Ingenieur
- Ingersoll Rand
- Injured reserve list
- Inland Revenue Department (disambiguation)
- Institutional repository
- Institutional research
- Instruction register
- Insulin receptor
- Insulin resistance
- Integrated resort
- InterRegio
- Interest rate
- Intermediate representation
- Internal router
- International Rectifier
- International Relations (journal)
- International Rescue (disambiguation)
- International relations
- International rules football
- Interventional radiology
- Inverted repeat
- Investor relations
- Ionizing radiation
- Ir (cuneiform)
- Ir (newspaper)
- Iran
- Iran Air
- Iridium
- Israel Railways
- Istro-Romanian language
- Portable appliance testing
- Real number
- Ta'Oi language