The .38 Smith & Wesson Special (commonly .38 Special, .38 Spl, or .38 Spc, pronounced "thirty-eight special") is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although some semi-automatic pistols and carbines also use this round. The .38 Special was the standard service cartridge of most police departments in the United States from the 1920s to the early 1990s, and was also a common sidearm cartridge used by soldiers in World War I. In other parts of the world, it is known by its metric designation of 9×29.5mmR^[6] or 9.1×29mmR.

Noted for its accuracy and manageable recoil, the .38 Special remains the most popular revolver cartridge in the world more than a century after its introduction.  It is used for target shooting, formal target competition, personal defense, and for hunting small game.