S.T.A.L.K.E.R.: Clear Sky, is the stand-alone prequel for S.T.A.L.K.E.R.: Shadow of Chernobyl, a first-person shooter computer game by Ukrainian developer GSC Game World. During E3, it was reported that the game will consist of a 50/50 mix of old remade/altered levels and totally new areas to explore. It will be released August 29, 2008. Also the game engine is being updated to v1.5 and will include DirectX 10 support. The AI is to receive an overhaul to accommodate the new "faction wars" feature; which will give players the opportunity to lead one of the eight factions to become rich and dominant.

The current tagline appears to be, as of writing, "What awaits you, S.T.A.L.K.E.R, in the Zone that changed?" On Thursday, March 27, 2008, GSC Game World announced the release date is currently set for August 29, 2008.