A4

A4 is generally used to refer to the A4 paper size.

A4, A04, A.IV, A.4 or A-4 may also refer to:
* A04, Encyclopaedia of Chess Openings code for Réti Opening
* "A-4 Helldiver", the civil version of the Curtiss Falcon an attack aircraft manufactured by Curtiss Aircraft Company
* A-004, the sixth and final abort test of the Apollo spacecraft
* A-4 Skyhawk, a 1954 attack aircraft manufactured by Douglas Aircraft Company
* ATC code A04, a division of the Anatomical Therapeutic Chemical Classification System
* Audi A4, a 1994 Audi luxury compact executive car
* Bavarian A IV, a 1852 German steam locomotive model
* Breda A.4, a 1926 Italian biplane trainer aircraft
* HMNZS Kahu (A04), a 1978 Royal New Zealand Navy Moa class inshore patrol vessel
* HMS "A4", an A-class submarine of the Royal Navy
* LNER Class A4, a class of steam locomotives, including the famous "Mallard"
* PRR A4, an American
* Prussian A 4, a 1913 German railbus
*The musical note A at formatnum:400 Hertz, also known as A-440.
* USS "Moccasin" (SS-5), a "Plunger"-class submarine of the United States Navy, which was renamed A-4 on 17 November 1911

And also :
* a climbing grade
* Southern Winds Airlines, the defunct Argentine airline, as its IATA code
* V-2 rocket, as the actual model number for the German weapon
* The code for permission to use specific land or premises for pubs and bars in town and country planning in the UK
* A4, the designation for air force headquarters staff concerned with logistics
** In the United Kingdom, the A4 Air Logistics branch of the UK Joint Force Air Component Headquarters
* The Alternating group acting on four elements
* A 4, a Swedish regimental designation (4th Artillery Regiment) that has been used by the following units:
** Gotlands artilleriregemente (unknown–1892)
** Norrlands artilleriregemente (1893–1997)

Roads

A4 is the name of several roads:; highways :
* A4 (Croatia), a highway connecting Zagreb to Hungary
* A4 highway (Lithuania)
* Route A4 (also known as Esk Highway), a state highway in Tasmania

; motorways :
* A4 autoroute (France), a highway connecting Paris to Strasbourg as part of the European routes E50 and E25
* Autostrada A4 (Italy), a part of the autostrada connecting Torino to Trieste
* Bundesautobahn 4, a Bundesautobahn between Aachen and Görlitz, part of the E 40, which connects Calais and Ridder in Kazakhstan
* A4 motorway (Luxembourg), in southern Luxembourg
* A4 motorway (Netherlands), a motorway in the Netherlands connecting Amsterdam, The Hague and Rotterdam
* A4 motorway (Portugal), a highway connecting Amarante to Porto
* A4 motorway (Slovenia)
* A4 motorway (Switzerland), connecting Schaffhausen to central Switzerland
* A4 (Romania), a planned motorway in Romania
* Autostrada A4 (Poland), an incomplete motorway intended to connect Zgorzelec to Korczowa through Wroclaw and Kraków, part of E40
* Autovía A-4, a Spanish autovía connecting Madrid to the Andalusia region
* Interstate A-4 in Alaska, United States
* Ostautobahn in Austria

; roads :
* A4 road (England), connecting London to Avonmouth, Bristol
* A4 road (Isle of Man), a primary road which connects Peel with Kirk Michael
* A4 road (Northern Ireland) in Northern Ireland
* A4 road (Zimbabwe), a highway between Beitbridge and Masvingo
* A004, National Route A004 (Argentina)
* A4 national road (Latvia), a beltway around Riga