The Ruger Standard Model is a rimfire semi-automatic pistol introduced in 1949 as the first product manufactured by Sturm, Ruger & Co., and was the founding member of a product line of .22 Long Rifle cartridge handguns, including its later iterations: the MK II, MK III, and MK IV. It is marketed as an inexpensive .22 caliber rimfire intended for casual sport and target shooting, and plinking. Designed by company founder William B. Ruger, the Standard model and its offspring went on to become the most accepted and successful .22 caliber semi-automatic pistols ever produced.