IR or Ir may refer to:

• Ir (newspaper), Latvian weekly newspaper
• Imperator: Rome, a 2019 video game published by Paradox Interactive
• Integrated resort, a euphemism for a casino in Singapore
• International Relations (journal), an academic journal
• I.R. Baboon, a fictional character in the cartoon series I Am Weasel

• Iarnród Éireann (Irish Rail), national passenger and freight railway system of the Republic of Ireland
• Illinois Railway, US
• Indian Railways, state-owned railway company of India
• InterRegio, part of Swiss Federal Railways
• IR Ishikawa Railway, local railway company in Ishikawa, Japan
• Iran Air (IATA airline code IR)
• Israel Railways, state-owned railway company of Israel

• Ingersoll Rand (NYSE trading symbol IR)
• International Rectifier, a former manufacturer of power semiconductors
• Independent-Republican Party of Minnesota, former name of the Republican Party of Minnesota

• Incidence rate (market research)
• Interest rate, or (when referring to an asset class) interest rate derivative
• Information ratio, when referring to risk-adjusted returns of a financial security
• Investor relations, a management responsibility in which companies disclose information for regulatory compliance and for bond/share-holders to make investment judgments

• Ir (cuneiform), a sign in cuneiform writing
• Ir language, also known as Ta'Oi language, spoken in parts of Laos and Vietnam
• Istro-Romanian language

• Indian Reserve, a section of land in Canada that is controlled by an Indigenous band government
• Iran, by ISO country code

• Immediate-release, related to time release technology in pharmaceuticals
• Incidence Rate, in epidemiology
• Insulin receptor, a transmembrane receptor that is activated by insulin
• Insulin resistance, a pathological condition
• Interventional radiology and interventional radiologist, an independent medical specialty
• Inverted repeat, a sequence of nucleotides that is the reversed complement of another sequence further downstream

• .ir, the Internet country code top-level domain for Iran
• Adobe ImageReady, a bitmap graphics editor shipped with Adobe Photoshop by Adobe Systems
• Image retention, the LCD and plasma display equivalent of screen burn
• Information retrieval, the science of searching for information in or as documents or databases
• Information revolution, one of the theoretical frameworks within which trends in current society can be conceptualized
• Institutional repository, a digital collection for preserving the intellectual output of an institution
• Institutional research, the collection, analysis, and reporting of institutional data
• Instruction register, part of a CPU's control unit
• Intermediate representation, a computer data structure
• Internal router

• Imaginary numbers, in mathematics, denoted ${\displaystyle {\text{i}}\mathbb {R} }$ or iR
• Infrared, a portion of the electromagnetic radiation spectrum
• Impulse response, an output function of a dynamic system presented with a brief input signal
• Insulation resistance, a measure of insulation material performance
• Ionizing radiation
• Iridium, symbol Ir, a chemical element

• Imperial–royal, abbreviation applied to institutions of the Austrian Empire
• Industrial relations, relations between management and workers in industry
• Ingenieur, abbreviated ir., an engineer's degree awarded by technical universities in the Netherlands, Belgium, Indonesia, and Malaysia
• Injured reserve list, a list of professional sports players who are injured and unable to play for an extended time
• International relations, in political science, the study of foreign affairs of and relations among states
• International rules football a hybrid code of football

• ${\displaystyle \mathbb {R} }$, the symbol of the set of real numbers in mathematics
• Inland Revenue Department (disambiguation), a government revenue service in several countries
• International Rescue (disambiguation)
• IRS (disambiguation)

This disambiguation page lists articles associated with the title IR.
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