MR

MR, Mr, mr, or mR may refer to:
 * Mr., an honorific title before any man's name

Arts, entertainment, and media

 * MR (Marina and Rainer), a 1989, one-act, multilingual opera libretto by Nikolai Korndorf
 * Mr. (band), a Hong Kong pop-rock band
 * Magyar Rádió, a Hungarian radio station
 * Mixed reality, the merging of real and virtual worlds in digital visualisation
 * Model Railroader, an American hobby magazine
 * Meta Runner, an Australian web series

Businesses and organisations

 * Chief Maqoma Regiment, an infantry regiment of the South African Army
 * Mineral Resources, Australian mining company
 * Mouvement radical (Radical Movement), a French political party
 * Mouvement Réformateur (Reformist Movement), a Belgian political party
 * Martin Research, a defunct American computer company

Education

 * mr., an academic degree, equivalent to Master of Laws, meester in de rechten, in Belgium and the Netherlands
 * Menntaskólinn í Reykjavík, a junior college in Iceland

Identification codes

 * Air Mauritanie (by IATA code)
 * Marathi language (by ISO 639-1)
 * Martinique (World Meteorological Organization country code)
 * Mauritania (ISO 3166-1 alpha-2 and FIPS 10-4 country codes)
 * .mr, the top-level Internet domain for Mauritania
 * Morocco (Library of Congress MARC country code)

Law

 * Master of the Rolls, the President of the Court of Appeal of England and Wales, Civil Division, and Head of Civil Justice
 * mr., an academic degree, equivalent to Master of Laws, meester in de rechten, in Belgium and the Netherlands

Medicine

 * Magnetic resonance imaging
 * Mental retardation, generalised learning or intellectual disability, in now obsolete jargon
 * Mineralocorticoid receptor, a human protein
 * Mitral regurgitation of blood flow in the heart
 * Modified release

Science

 * Magnetoresistance, change in electrical resistance due to a magnetic field
 * Mendelian randomization, a way of using genetic information to estimate causal effects
 * Merge request in software development
 * Millirem, a unit of radiation dose
 * Molecular replacement, a method of solving the phase problem in X-ray crystallography
 * Relative molecular mass, mass of a given molecule, Mr

Transport

 * M.R. (automobile), a microcar model built in 1945
 * Air Mauritanie (by IATA code)
 * Midland Railway, a United Kingdom railway
 * Nissan MR engine
 * Rear mid-engine, rear-wheel-drive layout, an automotive layout