American Colonization Society

American Chemical Society, an American professional association

Anglo-Chinese School, Singapore

Adam Carolla Show, American morning radio program

American Cryonics Society

Apolyton Civilization Site

Association of Caribbean States

Acute coronary syndrome, a form of chest pain due to reduced oxygen supply to the heart muscle

Advanced Camera for Surveys, an instrument aboard the Hubble Space Telescope

Alternative Community School, former name of Lehman Alternative Community School of Ithaca, New York, United States

American Cancer Society, an American medical organization

Alternative compensation system

ACS is a three-letter acronym that may refer to:

Alaska Communications System, former name of AT&T Alascom, an American communications services company

Aerial Common Sensor, a reconnaissance aircraft airframe developed by Lockheed Martin

Association of Cricket Statisticians and Historians

Actividades de Construcción y Servicios, S.A. (IBEX-35 stock symbol: ACS) Madrid, Spain

Adventure Construction Set

ACS International Schools, formerly American Community Schools, a group of schools in southern England

American Constitution Society for Law and Policy, or simply "American Constitution Society", a non-profit educational organization

Australian Computer Society

American College of Sofia, a Bulgarian secondary school

Affiliated Computer Services (stock symbol: ACS), a business and technology outsourcing company

Assumption College School

Army Combat Shirt, an American military uniform item.

Auxiliary Crane Ship (US Navy hull classification symbol)

American Community Survey, a project of the U.S. Census Bureau

Australian Customs Service

Avery Coonley School, a private k-8 school in Downers Grove, Illinois

Australian Cinematographers Society

Alaska Communications Systems, an American communications services company, distinct from "AT&T Alascom"

Associated Colleges of the South (United States)

Advanced Composites Solutions, engineering company specialized in composite materials technology

Air Cess (Liberia), from its ICAO airline designator

American Community Schools, an English-speaking private school system in Athens, Greece

Anglo-Chinese Schools, Malaysia

Action Code Script, a scripting language used in video games such as HeXen and modern Doom ports

ACS-1 and ACS-360, a supercomputer designed (but never completed) by the IBM Advanced Computing Systems group in the 1960s

Antichrist Superstar, a rock album by Marilyn Manson