A3, A03 or A.III may refer to: A3 paper, a paper size defined by ISO 216 Biology A3 regulatory sequence, a sequence for the insulin gene Adenosine A3 receptor, a human gene Annexin A3, a human gene ATC code A03 Drugs for functional gastrointestinal disorders, a subgroup of the Anatomical Therapeutic Chemical Classification System Brachydactyly type A3, a disease British NVC community A3 (Spirodela polyrhiza - Hydrocharis morsus-ranae community), a British Isles plants community Gibberellin A3, a plant hormone HLA-A3, a Human MHC Serotype HLA-A Subfamily A3, a rhodopsin-like receptors subfamily Urea transporter A3, a trans-membrane protein Games A3!, a Japanese video game and multimedia franchise A3 - Assault on the Aerie of the Slave Lords, a 1981 module for the Dungeons & Dragons fantasy role-playing game Alpha Trion, as the former name of this character from the Transformers Series Bird's Opening (A03), in chess, by the Encyclopaedia of Chess Openings code Music A3, a musical note, the A below Middle C Alabama 3, a band known as A3 in the U.S. to avoid confusion with the country group Alabama A-3, a Yamaha musical instrument product Sports A3 (classification), an amputee sport classification A3 Champions Cup, a club football tournament also known as the East Asian Champions Cup Arrows A3, a 1980 racing car A3, a climbing grade Vehicles A-3 lifeboat, a 1947 lifeboat for carrying by the SB-29 Superfortress Abrial A-3 Oricou, a French touring aircraft designed in 1927 Audi A3, a model of automobile Aussat (Optus) A3, a 1987 Australian telecommunication satellite Bavarian A III, an 1851 German steam locomotive model Chery A3, a compact car LNER Gresley Classes A1 and A3, a Pacific locomotive class designed by Sir Nigel Gresley Prussian A 3, a 1910 Prussian railbus SP&S Class A3, a 1914 steam locomotives class Weapons and military A-3 Falcon, a variant of the Curtiss Falcon, an attack aircraft manufactured by the Curtiss Aircraft Company A-3 Skywarrior, a strategic bomber manufactured by Douglas Aircraft Company AUG A3, a variant of the Austrian Steyr AUG rifle Fokker A.III, a 1915 armed version of the Fokker M.5 aircraft HMS A3, a British A-class submarine of the Royal Navy Kampfgeschwader 200, from its historic Geschwaderkennung code with the Luftwaffe in World War II Polaris A-3 missile, an American submarine-launched missile Wendes Artillery Regiment, a former Swedish Army artillery regiment, by designation A3, the staff designation for air force headquarters staff