AH

AH and variants may refer to:
 * Ah!, an exclamation
 * AH (Anno Hegirae), Latin for Islamic "in the year of the Hijra" similar to the Latin for the Christian year Anno Domini

Music

 * "Ah", song by Charles Aznavour written by Charles Aznavour and José Lucchesi 1954
 * "Ah" (song), a Japanese song by Superfly
 * "Ah", a song by the Turkish band Duman 2002

Games and literature

 * Achievement Hunter, a Texas-based online video gaming community
 * Adam Hughes, a comic artist who signs his work "AH!"
 * Alternate history, a subgenre of speculative fiction
 * Arcana Heart, a video game series
 * Avalon Hill, makers of military-themed board games

Places

 * Afghanistan, World Meteorological Organization country code
 * Anhui, a province of China (Guobiao abbreviation AH)
 * Austria-Hungary, a former European empire

Aviation

 * Air Algérie IATA designator
 * Artificial Horizon, an attitude indicator, a cockpit instrument (Aviation)
 * Bell AH-1 Cobra, a model of attack helicopter
 * Boeing AH-64 Apache, a model of attack helicopter

Computing

 * AH register, the high byte of an X86 16-bit AX register
 * Authentication Header (AH), a part of the IPsec protocol suite

Disease, ventilation and electricity

 * Adenomatous hyperplasia; see endometrial adenomatous hyperplasia and atypical adenomatous hyperplasia
 * Air handler, or air handling unit (AHU), a device used to condition and circulate air
 * Ampere hour, a unit of electric charge

Other fields

 * Aegyptiaca Helvetica, an archaeological journal published by Schwabe (publisher)
 * Ah (digraph), a digraph used in Taa language orthography
 * Albert Heijn, a Dutch supermarket chain owned by Ahold
 * Alkotmányvédelmi Hivatal, the Constitution Protection Office, a Hungarian intelligence agency
 * Asian Highway Network, a project among countries in Asia and Europe to improve the highway systems in Asia
 * A US Navy hull classification symbol: Hospital ship (AH)