Counter-Strike: Condition Zero (CS:CZ or CZ) is a multiplayer video game and the follow-up to Counter-Strike. The game was released in 2004 using the GoldSrc Half-Life engine. CS:CZ features a multiplayer mode, which features updated character models, textures, maps and other graphical tweaks. Unlike other Counter-Strike  games, Condition Zero also contains a single-player mission pack with the player unlocking maps and more efficient bots as they pass certain requirements for each map while playing as a counter terrorist. These requirements include targets such as "kill 3 enemies with a glock" or "win a round in 45 seconds". Condition Zero also introduces the Counter-Strike bot.

As of 2008, the game is one of the ten most played Half-Life modifications in terms of players, according to GameSpy.