B4

B4, B04, B.IV or B-4 may refer to:
* B4 or B4 II, a virtual synthesizer for Hammond organ (B-3) sound emulation (product of Native Instruments)
* B4 lens mount, a specification of lens mount, use for profession video cameras such as Betacam, and more
* B4 (music show), an early morning pop promo show on Channel 4 TV, produced by The Chart Show
* B4 (New York City bus) serving Brooklyn
* B4 road (Cyprus)
* B-4 (Star Trek), an android in the "Star Trek" fictional universe
* Alsace-Lorraine B 4, a Alsace-Lorraine P 1 class steam locomotive
* Auster B.4, a 1951 unusual British development of the Auster family of light aircraft
* Bavarian B IV, a 1852 German steam locomotives
* Bensen B-4, a
* CBSCR Class B4, a Cork, Bandon and South Coast Railway Irish steam locomotive
* HMS "B4", a B-class submarine of the Royal Navy
* Keystone B-4, a United States Army Air Corps biplane bomber
* Leukotriene B4 receptor and Leukotriene B4 receptor 2, two human genes
* Lohner B.IV, an aircraft
* LSWR B4 class, a 1891 British dock tank
* PRR B4, an American
* Subaru B4, the name with which the Subaru Legacy is marketed in Israel
* SM "UB-4", a 1915 German U-boat
* Vitamin B4, an alternate name for adenine
* 203-mm howitzer M1931 (B-4), a World War II Soviet ordnance piece

and also :
* an international standard paper size (250×353 mm), defined in ISO 216
* a subclass of B-class stars
* a level of vehicle armour
* an Internet shorthand for "before"
* Babylon 4 space station, the predecessor to the Babylon 5 station from the "Babylon 5" television series
* B.A.C.H. Flugbetriebs IATA airline designator (ICAO BCF)
* Bankair IATA code, ICAO airline designator (BKA)
* Flyglobespan IATA airline designator
* B04 : Alekhine's Defence chess code