AC, A.C., A/C, or Ac most often refers to:

• Air conditioning, often abbreviated as A/C
• Alternating current, a type of electrical current in which the current repeatedly changes direction

AC, A.C., A/C, or Ac may also refer to:

• Ace Combat, a series of combat flight simulator games
• Animal Crossing, a series of community simulation games
• Anonymous;Code, a visual novel in the Science Adventure series
• Another Code, a series of adventure games
• Armored Core, a series of mecha-based third person shooter games
• Asheron's Call, a fantasy massively multiplayer online role-playing game
• Assassin's Creed, a series of action-adventure games
• Assetto Corsa, a racing simulator game
• Astral Chain, an action-adventure hack and slash game
• Armor class, a combat-related parameter in the Dungeons & Dragons role playing game system
• A.C., a character in Fortnite: Save the World

• A. C. Newman, solo stage name for Canadian musician Carl Newman
• AC/DC, an Australian rock band formed in Sydney in 1973
• Adult contemporary music, a genre description used mainly in radio broadcasting
• Adult Contemporary (chart)
• Anal Cunt, an American musical group

• AC Comics, a comic book publisher established in 1969
• A.C. Slater, a fictional character in the American sitcom Saved by the Bell
• After Colony, an alternate timeline in the Gundam metaseries for the universe of Gundam Wing
• AC, the name of the "ultimate computer" in Isaac Asimov's novel The Last Question
• Asianovela Channel, a defunct Filipino TV channel

• AC Cars, a British specialist automobile manufacturer
• AC Spark Plug, Delco, AC-Delco, and ACDelco, automotive parts brands owned by General Motors
• AC Hotels, a hotel chain owned by Marriott International
• AC Restaurants, a hotel and restaurant chain in the Benelux
• Air Canada, the flag carrier and largest airline of Canada (IATA code AC)
• Allis-Chalmers, a former industrial conglomerate
• Anderson, Clayton and Company, former American cotton trading firm
• Associated Content, an online publisher and distributor of original content
• Ayala Corporation, a holding company (Philippine Stock Exchange symbol AC)

• Action Congress of Nigeria, a political party
• Advisory Council on Youth, a non-governmental decision-making body in the Council of Europe.
• Alternative for Change (Alternativa por el Cambio), a political party in Nicaragua
• Coast Alliance (Alianza Costeña), a former regional political coalition in Nicaragua

• AC – The Danish Confederation of Professional Associations, an umbrella organisation for several Danish trade unions
• AC Transit, a regional public transit agency in the San Francisco Bay Area
• Ad Council Japan (AC Japan), an organization that distributes Japanese public service announcements
• Athletics Canada, the governing body of athletics in Canada
• Civic Alliance Foundation (Alianţa Civică), a Romanian non-governmental organization
• Anthrocon, a furry convention held in Pittsburgh, Pennsylvania, US
• Audit Commission (Hong Kong), a government department in Hong Kong Special Administrative Region
• Aryan Circle, a white supremacist, Neo-Nazi prison gang spread throughout many U.S. correctional facilities

• AC Bonifacio (born 2002), a Philippine-Canadian actress, singer and dancer
• A. C. Green (born 1963), retired professional basketball player
• A. C. Grayling (born 1949), British philosopher
• Al Cowlings (born 1947), retired American football player
• Nickname for Andreas Christensen (born 1996), Danish footballer

• .ac, Internet top-level domain name for Ascension Island
• Aachen, a spa town in North Rhine-Westphalia, Germany
• Acre (state), Brazil
• Aleksandrovac, Serbia (vehicle registration plate code AC)
• Antigua and Barbuda, obsolete two-letter FIPS and NATO codes
• Atlantic City, New Jersey, US

• Aelod y Cynulliad, title for Members of the National Assembly for Wales
• Aircraftman, an air forces rank
• Ashoka Chakra (military decoration), India's highest peacetime military decoration
• Assistant Commissioner of Police of the Metropolis, a rank in London's Metropolitan Police
• Companion of the Order of Australia
• First assistant camera or Second assistant camera, in film-making
• Aviation Cadet, a military rank sometimes written as A/C

• Acromioclavicular joint (AC joint), the shoulder junction between the scapula and the clavicle
• Adenylate cyclase, a lyase enzyme
• Adriamycin and cyclophosphamide, a chemotherapy regimen used to treat breast cancer
• Ante cibum (ac), Latin for "before meal", commonly seen in medical prescriptions
• Anterior commissure, a bundle of nerve fibers connecting the two temporal lobes of the brain
• Anterior cruciate ligament (AC ligament or ACL), a major ligament in the knee
• Appropriateness criteria, when it is appropriate to perform a medical procedure or service
• Assist control, a former term for continuous mandatory ventilation, a mode of mechanical ventilation
• Adenocarcinoma, a type of cancerous tumor
• Allergic conjunctivitis, inflammation of the conjunctiva

• Acetyl group, a functional group in chemistry
• Actinium, symbol Ac, a chemical element
• Hydrogen cyanide, AC in chemical weapons classification

• .ac, Internet top-level domain name for Ascension Island
• .ac (second-level domain), Internet second-level domain used to denote academic institutions in many countries
• AC (complexity), a hierarchy of complexity classes found in circuit complexity
• AC, initialism of access control
• Artificial consciousness, a field related to artificial intelligence and cognitive robotics
• Authorization certificate or attribute certificate, a digital permission to use a service or resource
• Arithmetic coding, a form of entropy encoding used in lossless data compression
• Alternating component a.k.a. AC coefficient in discrete cosine transform
• IEEE 802.11ac-2013, a wifi standard using 5 GHz, released in Dec 2013

• Altocumulus cloud, a medium-level cloud type
• Anticipated convection, convective outlooks issued by the U.S. National Weather Service

• Air conditioning, technologies for altering the temperature and humidity of air
• Across corners (A/C), a measure of external diameter of hexagonal nuts
• Alternating current, a type of electric current
  • AC power, a net transfer of energy over a complete cycle of the alternating current waveform
• Asphalt concrete, a type of road or path surfacing
• Average cost, in economics
• Axiom of choice, a mathematical concept in set theory
• A US Navy hull classification symbol: Collier (AC)

• Ac (rune) (ᚪ), a rune of the Anglo-Saxon fuþorc and a continuation of the Elder Fuþark ansuz
• Abkhazian Cup, football cup competition in Abkhazia
• AC Milan, an Italian football club based in the city of Milan
• Acre, a unit of area with the symbol ac
• Advisory circular, a publication to provide guidance for compliance with airworthiness regulations
• After Christ, known as the Common Era (CE)
• Ante Christum or A.C., a Latin term meaning "before Christ"
• Antichrist, a Biblical prophecy about one who will oppose Jesus Christ and substitute himself in Christ's place
• Appeal Cases, or A.C., a UK law reporter covering decisions of the House of Lords, Supreme Court, Privy Council, and Court of Appeal
• Ancol railway station, a railway station in Jakarta, Indonesia
• Ards Circuit, motorsport racing circuit
• Armor class, a common property in role playing games used to determine the amount of armor a character has
• Army Corps, an operational formation, sometimes known as a field corps, which consists of two or more divisions
• Atlantic College, an international IB Diploma Programme residential Sixth Form College in the Vale of Glamorgan in Wales
• Auto Calesa, a war-time short-body version of the Philippine jeepney

• All pages with titles containing AC or ACs
• All pages with titles beginning with AC
• AC/DC (disambiguation)