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, 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 polytope, H₄, a symmetry group in the Five-dimensional space, fifth dimension.

Technology

* H-4 SOW, a precision-guided glide bomb used by the Pakistan Air Force * Halo 4, a video game created by 343 Industries for the Xbox 360 * Harrison Number Four, 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#heading

Transport

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#Automobile use, "flat four" engine (not to be confused with an actual H 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 * H4, IATA code for Héli Sécurité Helicopter Airlines, based in France * H4, IATA code for Inter Islands Airlines, based in Cape Verde

Ships and submarines

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

Trains

* GNR Class H4, a 1920 British 2-6-0 steam locomotive model

Other uses

* H4 (film), ''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 * H-4, a huge eruption of the Hekla volcano around 2310 BC * H4, Houston Hash House Harriers, a social running club based in Houston, Texas