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