| Acronym | Definition |
|---|
| IR | Infrared |
| IR | Iran |
| IR | International Relations |
| IR | Imposto de Renda (Brazil) |
| IR | Investor Relation |
| IR | Injured Reserve (football) |
| IR | Intermediate Representation |
| IR | Irish (linguistics) |
| IR | Immune Response |
| IR | Islamic Republic of Iran (ISO country code, top level domain) |
| IR | Information Required |
| IR | Interest Rate (economics) |
| IR | Institutional Research |
| IR | Ingersoll-Rand (pneumatic products company) |
| IR | Islamic Republic |
| IR | Engineer (University, Dutch) |
| IR | Inland Revenue (UK) |
| IR | Islamic Relief (UK) |
| IR | Insulation Resistance |
| IR | Image Runner |
| IR | Information Retrieval |
| IR | Industrial Relations |
| IR | Institutional Repository (digital intellectual output) |
| IR | Insulin Resistance |
| IR | Instrument Rating (Aviation) |
| IR | Indian Reservation |
| IR | Infrared Radiation |
| IR | Immediate Release (pharmaceutics) |
| IR | Impôt sur le Revenu (French income tax) |
| IR | Impulse Response (radio propagation) |
| IR | Indian Railway |
| IR | Iridium |
| IR | Information Resources |
| IR | Interface Repository |
| IR | Instruction Register |
| IR | Independent Research |
| IR | Insulin Receptor (molecular biology) |
| IR | Information Request |
| IR | Incidence Rate |
| IR | Incident Response (security) |
| IR | Initial Response (military logistics) |
| IR | Ingenieur (Dutch: Master of Science) |
| IR | Inspection Report |
| IR | Incident Report (Canadian Air Force) |
| IR | Information Requirements |
| IR | Information Report(s) |
| IR | Interventional Radiology (medicine) |
| IR | Ionizing Radiation |
| IR | Internal Resources |
| IR | Inter-Research |
| IR | Industrial Robot |
| IR | Im Ruhestand (German: Retired) |
| IR | Insuficiencia Renal (Spanish: Renal Failure) |
| IR | Information Revolution |
| IR | Imaging Radar |
| IR | Information Ratio |
| IR | Ischaemia-Reperfusion |
| IR | Instant Replay |
| IR | International Roaming (GSM technology) |
| IR | Internal Review |
| IR | Iran Air (IATA airline code) |
| IR | Information Repository (US EPA Superfund site information) |
| IR | Information Rate (US DoD) |
| IR | Issue Resolution (various organizations) |
| IR | Internal Resistance |
| IR | Intelligence Report |
| IR | Initialization and Refresh (compressor state) |
| IR | Internet Registry |
| IR | Ingestion Rate |
| IR | Index Register |
| IR | Infrared Radiometer |
| IR | Information Record |
| IR | Interrupt Request |
| IR | Independent Radio |
| IR | Investigation Report |
| IR | Iron Rod |
| IR | Inherited Runner (baseball; runner on base when a pitcher enters) |
| IR | Integrated Resort (Singapore) |
| IR | Internal Rotation |
| IR | Interventional Radiologist (medicine) |
| IR | Impairment Rating (medical assessment) |
| IR | Intermediate Reach |
| IR | Inner Radius (construction industry) |
| IR | InterRegio (train) |
| IR | Incident Record |
| IR | Intelligent Routing (computing) |
| IR | Inhalation Rate |
| IR | Installation Restoration |
| IR | Ileal Resection |
| IR | Intelligence Requirement (US DoD) |
| IR | Ice on Runway |
| IR | Internet Router |
| IR | Isoprene Rubber (polyisoprene rubber) |
| IR | Iterative Reconstruction |
| IR | Isoprene Rubber |
| IR | Image Rejection (radio electronics) |
| IR | Interracial Relationship |
| IR | Interference Rejection (communications systems) |
| IR | Incremental Reactivity |
| IR | Ivan Reitman (film director) |
| IR | Installation Report |
| IR | Instrument Reading |
| IR | Invoice Receipt (accounting) |
| IR | Integrated Resources |
| IR | Israel Railways |
| IR | Inspection Record |
| IR | Institut de Rééducation (French: Rehabilitation Institute; various locations) |
| IR | International Rendezvous (dating service) |
| IR | Interstate Route |
| IR | Inspection Request (construction) |
| IR | Investigation Request |
| IR | Industrial Roundtable |
| IR | InterReklama (Russian advertising network) |
| IR | Invitation Request |
| IR | Intensification Ratio |
| IR | Indigenous Revolution |
| IR | Inward Radial |
| IR | Interval Rate |
| IR | Internal Revision |
| IR | Investment Request |
| IR | Integrated Rating (marine) |
| IR | Internment/Resettlement |
| IR | Instrument Route |
| IR | Interoperability Requirement |
| IR | Ingress Router |
| IR | Intelligence Request |
| IR | Intermediate Resonance |
| IR | IFR Military Training Route |
| IR | Interposing Relay |
| IR | Investable Resources |
| IR | Intelligent Roaming |
| IR | Intermittent Reperfusion |
| IR | Intermediate Rear |
| IR | Induction Regulator |
| IR | Interruption Reporting |
| IR | IglooReport (Pittsburgh Penguins website) |
| IR | Imperator et Rex (Emperor and King) |
| IR | Internet Protocol Detail Record Recorder |
| IR | Incorrect Reconfiguration |
| IR | Incoherent Recombining |
| IR | Insurance Record(s) (insurance) |
| IR | Inhibiting Relay |