DEFCON (stylised as DEFCOИ and sometimes subtitled Everybody Dies in the North American version and Global Thermonuclear War in the European version) is a real-time strategy game created by independent British game developer Introversion Software. The gameplay is a simulation of a global nuclear war, with the game's screen reminiscent of the "big boards" that visually represented thermonuclear war in films such as Dr. Strangelove, Fail-Safe, and especially WarGames.

The game has been available by download since September 29, 2006 through Introversion's web store and Steam. On 5 April 2007, publisher Encore announced they would be publishing the game in the United States, and had ordered an initial 50,000 copies of the game for retail. In the UK it was released for retail on 15 June 2007 and for a limited period included the developer's first game Uplink.