ATR

ATR may refer to:

Medicine

 * Acute transfusion reaction
 * Ataxia telangiectasia and Rad3 related, a protein involved in DNA damage repair

Science and mathematics

 * Advanced Test Reactor, nuclear research reactor at the Idaho National Laboratory, US
 * Attenuated total reflectance in infrared spectroscopy
 * Advanced tongue root, a phonological feature in linguistics
 * Atractyloside, a toxin and inhibitor of "ADP/ATP translocase"
 * ATR0, an axiom system in reverse mathematics

Technology

 * Answer to reset, a message output by a contact Smart Card
 * Automatic target recognition, recognition ability
 * Autothermal reforming, a natural gas reforming technology

Transport

 * ATR (aircraft manufacturer) an Italian-French aircraft manufacturer
 * ATR 42 airliner
 * ATR 72 airliner
 * IATA code for Atar International Airport
 * Andaman Trunk Road
 * Air Transport Rack, standards for plug-in electronic modules in aviation and elsewhere; various suppliers e.g. ARINC
 * Atmore (Amtrak station), Amtrak station code ATR

Music

 * All That Remains (band), an American heavy metal band
 * Atari Teenage Riot, a German techno band performing "digital hardcore" music
 * ATR (song), a song by ATR

Organisations

 * Absent Teacher Reserve, of teachers in New York City
 * Americans for Tax Reform
 * Anglican Theological Review

Other

 * African Traditional Religion
 * A US Navy hull classification symbol: Rescue tug (ATR)
 * ATR: All Terrain Racing, a video game
 * ATR.1 certificate, in trade between the European Union and Turkey
 * ATR (company) (Auto-Teile-Ring), Germany
 * Average True Range, a market volatility indicator
 * ATR (TV channel), a Crimean Tatar television channel in Ukraine