Garry's Mod (officially abbreviated to GMod) is a sandbox physics game that allows the player to manipulate objects and experiment with physics. Garry's Mod has been available on Steam's content delivery service since November 29, 2006. Despite being a standalone game, Garry's Mod requires the user to own at least one Source game on Steam such as Half-Life Source, Half-Life 2, Team Fortress 2, or Counter-Strike: Source. It is also commonly used for the creation and publishing of videos, mainly from Team Fortress 2, Portal and Left 4 Dead, on YouTube due to the wide range of features thumb|300px|right|PILLS!!!

thumb|300px|left|An example of a short video made with Garry's Mod. Note the character models are imported from Left 4 Dead. thumb|300px|right|Another example of a video made with Garry's Mod.