A3

A3, A03, A-3, A.III or A 3 can refer to:
* A-003, the fourth abort test of the Apollo spacecraft
* A3 Champions Cup, a club football tournament also known as the East Asian Champions Cup
* A3 (game), a game made by Korean company AniPark
* A3 regulatory sequence for the insulin gene
* A3 Trade International (Pvt.) Ltd, a exporter and importer of chemical, manpower, garments in Bangladesh
* A-3 Skywarrior, a strategic bomber manufactured by Douglas Aircraft Company
* Abrial A-3 Oricou, a French touring aircraft designed in 1927
* Adenosine A3 receptor, a human gene
* Aggregate series#A3, a German rocket design during World War II
* Annexin A3, a human gene
* ATC code A03, a a division of the Anatomical Therapeutic Chemical Classification System
* Audi A3, a model of automobile
* Bavarian A III, a 1851 German steam locomotive model
* Fokker A.III, a 1915 armed version of the Fokker M.5 aircraft
* HLA-A3, a Human MHC Serotype HLA-A
* HMS "A3", a British A class submarine of the Royal Navy
* LNER Gresley Classes A1 and A3, a Pacific Locomotive Designed by Sir Nigel Gresley
* PRR A3, an American
* Prussian A 3, a 1910 German railbus
* SP&S Class A3, a 1914 steam locomotives class

Roads and highways

There are several roads and highways with the designation A3:; highways :
* A3 highway (Croatia), an east-west highway in northern Croatia running between border crossings with Slovenia and Serbia and passing thorugh Zagreb, the capital of Croatia
* A3 highway (Lesotho), one of the main highways of Lesotho in southern Africa
* A3 highway (Lithuania)
* Interstate A-3, an interstate highway in Alaska
* Tasman Highway or A3, a state highway in Tasmania

; motorways :
* A3 motorway (Cyprus), connecting Larnaca and Ayia Napa
* A3 motorway (Luxembourg), in southern Luxembourg
* A3 motorway (Portugal), connecting Porto with Braga
* A3 motorway (Romania), a freeway, currently in construction, linking Transylvania with Bucharest
* A3 motorway (Slovenia), in western Slovenia
* A3 motorway (Switzerland), connecting Basel with Sargens and vice versa
* Autostrada A3 (Italy), connecting Naples with the Reggio Calabria and vice versa
* Autovía A-3, a Spanish autovía connecting Madrid with Valencia and vice versa
* Bundesautobahn 3, a German autobahn connecting Wesel with Passau and vice versa

; roads :
* South Australian State Route:
**
* A3 road (England), a trunk road connecting London with Portsmouth and vice versa
* A3 road (Isle of Man), a primary road which connects Castletown in the south of the island with Ramsey and vice versa
* A3 road (Northern Ireland), a road in Northern Ireland connecting Lisburn with Middletown and vice versa
* A3 road (Zimbabwe), a road in Zimbabwe
* A003, National Route A003 (Argentina)
* A3 national road (Latvia), a national road in Latvia

other

* A-3 Falcon, a variant of the Curtiss Falcon, an attack aircraft manufactured by the Curtiss Aircraft Company
* a paper size defined by ISO 216
* a musical note, the A below Middle C
* a climbing grade
* Alabama 3, a band known as A3 in the U.S. to avoid confusion with the country group Alabama
* The IATA code for Aegean Airways
* Tonga aircraft registration code
* Wendes artilleriregemente designation, a former Swedish Army artillery regiment
* A3, the designation for air force headquarters staff concerned with operations
** In the United Kingdom, the A3 Air Operations Branch of the Joint Force Air Component Headquarters
* USS "Grampus" (SS-4), a Plunger class submarine of the United States Navy
* In town and country planning in the United Kingdom, A3 is the code for permission to use specific land or premises for restaurants and cafés
* A3J, the original designation of the US Navy's A-5 Vigilante bomber
* Alpha Trion, as the former name of this character from the Transformers Series
* ARITH-MATIC, as the former name for this programming language
* A-3, a Yamaha combo organ
* A03, Encyclopaedia of Chess Openings code for Bird's Opening