AT may mean:
- Aarne-Thompson classification system
- AT Field, a force field in the anime Neon Genesis Evangelion
- Acceptance test
- Aero triangulation
- Air Trecks, fictional inline skates in the manga and anime Air Gear
- Alimentary tract
- Allied Telesyn
- Atmel Corporation
- Anaerobic threshold
- Análisis Transaccional (Spanish "Transactional analysis"), a psychological method
- Anguilla, a World Meteorological Organization country code
- Anti-tank weapons
- Counter-terrorism, also known as "anti-terrorism" (AT)
- Appalachian Trail
- Aphex Twin
- Appropriate Technology
- Ashmore and Cartier Islands (FIPS 10-4 territory code and obsolete NATO country code
- Assistive technology
- IBM Personal Computer/AT
- AT form factor for motherboards and computer cases
- The common name for the 5-pin DIN keyboard connector
- Ataxia telangiectasia, an immunodeficiency disorder
- Atchison County, Kansas (county code)
- Attack Team (game), a 2000 computer game
- Audit trail
- Austria's ISO, 2-letter country code
- .at is the Internet country code top-level domain for Austria
- Auto Trend
- Automatic transmission
- Aviation Electronics Technician (United States Navy ratings), an enlisted rating in the United States Navy
- Hayes command set for computer modems (all commands begin with the characters "AT")
- Royal Air Maroc (IATA airline designator)
- Abel Tasman, a seventeenth century Dutch explorer and merchant
At may mean:
- Ampere-turn (symbol), an International System of Units (MKS) unit of magneto-motive force
- Astatine, the chemical symbol for the element
- a subdivision equal to 1/100 of a Kip, the unit of currency in Laos
aT may mean:
- attotesla, an SI unit of magnetic flux density
at-preposistion at may mean:
- "@", the punctuation symbol now typically used in e-mail addresses
- at (Unix command), to schedule tasks to be performed at a later date
- technical atmosphere (symbol), physical unit of pressure
