AC-4 or AC4 may refer to:

Music

AC4 (band) AC4 is a Swedish hardcore punk band from Umeå, Sweden. Refused members Dennis Lyxzén and David Sandström had been talking about starting a new band for a long time. In the spring of 2008 Karl Backman had written songs for the new band and th ...

, a Swedish hardcore punk band, or their eponymous album

Vehicles

Aircraft

* Light Wing AC4, an aircraft *

Aviastroitel AC-4 Russia The Aviastroitel AC-4 Russia is a Russian mid-wing, single-seat glider designed by Vladimir Egorovich Fedorov and produced by Aircraft Cooperative Mechta, which became Aviastroitel, now Glider Air Craft. The aircraft is sometimes referred ...

, glider * Comte AC-4, a two-seat Swiss monoplane

Ships

* USS Cyclops (AC-4), a US Navy collier ship

Trains

* Southern Pacific class AC-4, a class of steam locomotive

Tanks

AC4 tank The AC4 (Australian Cruiser Tank Mk. 4) was a cruiser tank designed in Australia in World War II as the intended successor to the AC3 Thunderbolt. Like its predecessors the AC4 was to have a one piece cast hull and turret. The AC4's most import ...

a World War Two Australian cruiser tank.

Technology

* AC-4, an IEC Utilization Category *

Dolby AC-4 Dolby AC-4 is an audio compression technology developed by Dolby Laboratories. Dolby AC-4 bitstreams can contain audio channels and/or audio objects. Dolby AC-4 has been adopted by the DVB project and standardized by the ETSI. History Its develop ...

, Dolby Digital audio codec

Videogames

* '' Ace Combat 04: Shattered Skies'', a 2001 video game * ''

Armored Core 4 is a 2006 vehicular combat game developed by FromSoftware. It is the 12th installment and 4th main installment in the mecha-based ''Armored Core'' series, the game serves as a reboot for the franchise. It was released for the PlayStation 3 an ...

'', a 2006 video game * '' Assassin's Creed IV: Black Flag'', a 2013 video game