A remake/update of the original Counter-Strike, running on the Half-Life 2 Source engine. This title was made available through Valve's Steam downloading service in October of 2004, with a retail release in the Fall of 2005.

With a full complement of real world pistols, rifles and shotguns, Counter-Strike's battle of terrorists and counter-terrorists became the basic blueprint for many modern team-based online shooters. Now enhanced with the power of the Source engine, the game features drastically improved visuals, enhancements on classic maps, off-line skirmish play with AI bots and more.

The retail version of Counter-Strike: Source also includes Half-Life 2: Deathmatch and Day of Defeat: Source.