MR, Mr, mr, or mR may refer to:

• Mr., an honorific title of men

Arts, entertainment, and media

• MR (Marina and Rainer) (1989), a 1994 one-act chamber opera by Nikolai Korndorf
• Magyar Rádió, a Hungarian radio station
• Mixed reality, the merging of real and virtual worlds
• Model Railroader, a US hobby magazine
• Meta Runner, an Australian web series.

Identification codes

• .mr, the country code top level domain (ccTLD) for Mauritania
• Air Mauritanie (IATA code)
• Marathi language (ISO 639-1 code "mr")
• Martinique, country code (World Meteorological Organization)
• Mauritania, country code (ISO 3166-1 Alpha-2, FIPS 10-4)
• Morocco, country code (Library of Congress MARC standards)

Science

• Magnetoresistance, change in electrical resistance due to a magnetic field
• Mendelian randomization, a way of using genetic information to estimate causal effects
• Mental retardation
• Mineralocorticoid receptor
• Mitral regurgitation of blood flow in the heart

Transportation

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

Other uses

• Chief Maqoma Regiment, an infantry regiment of the South African Army
• Mr. (artist) (born 1969), Japanese artist
• Mr. (band), a Hong Kong pop rock band
• Master of the Rolls, the President of the Court of Appeal of England and Wales, Civil Division, and Head of Civil Justice
• Menntaskólinn í Reykjavík, junior college in Iceland
• Mouvement Radical (Radical Movement), a French political party
• Mouvement Réformateur, a Belgian political party

See also

• Magnetic resonance (disambiguation)
• Mister (disambiguation)