ACH may refer to:
In American banking:
- Automated Clearing House, an electronic banking network often used for direct deposit and electronic bill payment
A business or organization:
- Aluminum Corporation of China Limited
- ACH Food Companies, Inc., American subsidiary of Associated British Foods
- Automotive Components Holdings, LLC, a Ford-managed temporary company mandated to dispose of unprofitable operations of Visteon, its former parts division
- Alberta Children's Hospital, Calgary, Alberta
- Arkansas Children's Hospital, Little Rock, Arkansas
- AC Horsens, a Danish football club
- American College of Heraldry, an American heraldic organization
- Accion contra el Hambre, an NGO, part of the Action Against Hunger International Network
- Association for Computers and the Humanities
In biology, chemistry, and medicine:
- Acetylcholine (ACh), a neurotransmitter
- Adrenocortical hormone
- Achondroplasia, a genetic disorder that is a common cause of dwarfism
- Aluminium chlorohydrate, an aluminium inorganic polymer used as a flocculant for water purification
- Acetone cyanohydrin, a highly toxic organic compound
In transportation:
- Achnashellach railway station the National Railway code in the United Kingdom
- St. Gallen-Altenrhein Airport, Switzerland, IATA airport code
- Adelaide-Crafers Highway
- Angeles Crest Highway
- Anti-Condensation Heater
In linguistics:
- Acholi language (ach), ISO 639 code
In investigation:
- Analysis of Competing Hypotheses, an investigation methodology
In the United States military:
- Advanced Combat Helmet, or MICH TC-2000 Combat Helmet, worn by army soldiers
In heating, ventilation, and air conditioning:
- Air changes per hour, a unit in ventilation
Ach may refer to:
- Ach, Iran, a village in Qazvin Province
- Bregenzer Ach, a tributary of Lake Constance
- Dornbirner Ach, a tributary of Lake Constance
- Friedberger Ach, a tributary of the Lech
- Ach (Ammer), a tributary of the Ammer