ACH
ACH or Ach may refer to:

Businesses and organisations

Businesses
 ACH Food Companies, Inc., American subsidiary of Associated British Foods
 ACH Network, American electronic fund clearing house
 Automotive Components Holdings, LLC, a Ford-managed temporary company

Hospitals
 Adelaide Children's Hospital, former component of the Women's and Children's Hospital, Adelaide, South Australia
 Akron Children's Hospital, Akron, Ohio, U.S.
 Alberta Children's Hospital, Calgary, Alberta, Canada
 Arkansas Children's Hospital, Little Rock, Arkansas, U.S.

Organizations
 Accion contra el hambre, part of the Action Against Hunger network
 Association for Computers and the Humanities

People
 Ach (surname)
 ACH (wrestler), American professional wrestler Albert C. Hardie, Jr (born 1987)
 Ach., taxonomic author abbreviation for Erik Acharius (1757–1819), Swedish botanist

Places 
 Aach (toponymy), a term for "river" in German hydronymy
 Ach (Ammer), a tributary of the Ammer, Bavaria, Germany
 Ach (Blau), a tributary of the Blau, Baden-Württemberg, Germany
 Bregenzer Ach, a tributary of Lake Constance, Austria
 Dornbirner Ach, a tributary of Lake Constance, Austria
 Friedberger Ach, a tributary of the Lech, Bavaria, Germany
 Ach, Iran, a village in Qazvin Province

Science
 Acetone cyanohydrin, an organic compound
 Acetylcholine (ACh), a neurotransmitter
 Aluminium chlorohydrate, a group of water-soluble, specific aluminium salts

Sports
 AC Horsens, a Danish football club
 Allan Cup Hockey, a Canadian senior ice hockey league

Transportation
 Achnashellach railway station, Scotland, National Railway code ACH
 St. Gallen–Altenrhein Airport, Switzerland, IATA airport code ACH

Other uses
 Acholi dialect, ISO 639 code ach
 Advanced Combat Helmet, in the United States Army
 Air changes per hour, a measure of ventilation
 Analysis of competing hypotheses, a methodology 
 Automated clearing house, a network for processing transactions

See also
Aboriginal Cultural Heritage Act 2021, or ACH Act, in Western Australia