The story of Armored Core 4 takes place in an alternate universe where corporations have taken control of governmental institutions. As resources dwindle, the gap between the rich and the poor widens, leading to anarchy and a loss of government control. In response, six corporations engage in a full-scale war known as the Nation Dismantlement War, ultimately establishing a new order with the introduction of Pax Economica.
Five years into the Pax Economica era, players take on the role of a member of the Ravens, a rebel group seeking to challenge the modern slavery system. Equipped with a customizable mech, part of a squad, players must fight against corporations' mechs in 30 missions grouped into chapters. As each level is completed, new parts become available for assembly and repair can be done using wages earned during gameplay. Multiplayer options are also available through PlayStation Network and Xbox Live.