AC4 are a hardcore band from Umeå, Sweden formed in 2008. Consisting of ex-Refused members Dennis Lyxzén and David Sandström and two friends of them, Jens Nordén and Karl Backman they have toured mainly around Sweden so far and have already recorded one self-titled album and will release a new EP in 2010. The name of the band originates from the regional code of the county Umeå is located in.