Counter-Strike: Condition Zero is a multiplayer shooter video game, the sequel to the cult classic, Counter-Strike. The game has been stuck in development hell for quite a while, and while it changed multiple developers more than once, it was finally released in 2004 and it used the GoldSrc engine.

Counter-Strike: Condition Zero is basically CS 1.6 but with a single player campaign with intelligent A.I. that was challenging and difficult to beat, especially in some missions. The game has a multiplayer mode, and it features updated character models, updated textures, maps, and various other graphical tweaks which increased the game's graphical appeal when compared to the previous game. Counter-Strike: Condition Zero has two single-player campaigns which are filled with chaotic action and thrilling missions, as well as Condition Zero: Deleted Scenes which has some of the most difficult and challenging missions found in the game.

The game got ported to OS X and Linux in 2013. Various graphical improvements which were made by Gearbox include alpha blending (which allows for better weather effects and more realistic foliage), as well as the addition of various explosive weapons such as the tear gas bomb, the Molotov cocktails, and the immensely powerful M72 LAW rocket. The Steam release also allowed the developers to constantly update the game in order to prevent cheating.