Turtle Rock Studios is a video game development company known for their work on Counter-Strike: Condition Zero as well as Left 4 Dead. It was founded in March 2002 by Michael Booth. They were acquired by Valve on January 10, 2008, and renamed Valve South during late development of Left 4 Dead. Some time after the release of Left 4 Dead, Turtle Rock Studios put up a new website declaring they have left Valve and are once again working on video games as an independent studio.
- Counter-Strike (Xbox)
- Counter-Strike: Condition Zero
- Counter-Strike: Source (AI and maps)
- Left 4 Dead (game and The Lighthouse, Crash Course and The Sacrifice add-ons)
- Left 4 Dead 2 (The Sacrifice add-on)
- Leap Sheep!