Which Counter-Strike game was the first to use Valve’s Source engine?

Counter-Strike: Source was the first Counter-Strike game to use Valve’s Source engine.

Released in 2004, Counter-Strike: Source rebuilt the original competitive shooter on the Source engine, which Valve had introduced with Half-Life 2. The move brought updated graphics, physics, lighting, and map technology while preserving the series’ team-based bomb-defusal and hostage-rescue gameplay.

The game existed alongside the older GoldSrc-based Counter-Strike 1.6 for years. That overlap created a long-running distinction between the classic version and the Source version, particularly in communities that preferred different movement, shooting, and map behavior.

Counter-Strike: Global Offensive later used an updated version of the Source engine, while Counter-Strike 2 moved the series to Source 2. Thus, CS: Source is the key transition point between the original engine technology and Valve’s later revisions.