H4

H4, H04, or H-4 may refer to:

Science and mathematics

 * ATC code H04 Pancreatic hormones, a subgroup of the Anatomical Therapeutic Chemical Classification System
 * Histamine H4 receptor, a human gene
 * Histone H4, a protein involved in the structure of chromatin in eukaryotic cells
 * Hydrogen-4 (H-4), an isotope of hydrogen
 * H4, a symmetry group in the fifth dimension; see H4 polytope
 * H-4, a huge eruption of the Hekla volcano around 2310 BC

Technology

 * H-4 SOW, a precision-guided glide bomb used by the Pakistan Air Force
 * H4 (chronometer), an 18th-century marine chronometer designed by John Harrison
 * Zoom H4 Handy Recorder, a handheld digital audio recorder
 * , level 4 heading markup for HTML Web pages, see HTML element

Automobiles and roads

 * H4, a halogen headlamp bulb
 * H4, development name of the Hummer HX concept car
 * H-4, shorthand for a 4-cylinder horizontally-opposed or "flat four" engine
 * H4 Dansteed Way, a road in Milton Keynes, England

Aviation

 * GEN H-4, a Japanese helicopter design
 * Hughes H-4 Hercules (Spruce Goose), the largest flying boat ever built
 * Héli Sécurité Helicopter Airlines (IATA code), based in France; see List of airline codes (H)
 * Inter Islands Airlines (IATA code), a former airline  based in Cape Verde

Ships and submarines

 * HMS H4, a 1915 British Royal Navy H-class submarine
 * HMS Tenedos (H04), a 1918 British Royal Navy Admiralty S-class destroyer
 * USS H-4 (SS-147), a 1918 United States Navy submarine

Rail

 * GNR Class H4, a class of British steam locomotives

Other uses

 * Halo 4, a video game created by 343 Industries for the Xbox 360
 * H4 (film), a 2013 film
 * H-4 visa, issued by the U.S. Citizenship and Immigration Services
 * British NVC community H4, a heath community in the British National Vegetation Classification system
 * H4 (classification), a cycling classification used in para-cycling