9×23

The 9×23mm Steyr is a rimless pistol cartridge developed in Austria in the early 20th century. It was designed by the Steyr-Werke company for use in their pistols, most notably the Steyr M1912. The cartridge features a bottlenecked case, which is unusual for a pistol round. This design allowed for a higher propellant charge and thus greater muzzle velocity and energy compared to contemporary straight-cased pistol cartridges. The bottleneck shape also facilitated reliable feeding from the pistol's magazine.

The 9×23mm Steyr saw limited military adoption, primarily by the Austro-Hungarian Army and later by Austria and its successor states. It was also used by some police forces and civilian shooters. The cartridge's performance was considered quite potent for its time, offering superior range and penetration. However, its complex case design made it more expensive to manufacture than standard straight-walled cartridges. Production of the 9×23mm Steyr largely ceased after World War II. While no longer a common military or police round, it is still occasionally encountered by collectors and enthusiasts of vintage firearms. Ammunition is produced by some specialty manufacturers for the historical firearms that chamber this round.