The .9mm Steyr Ammo, also known as the 9x23mm Steyr Ammo, is a centerfire pistol bullet that was initially created for Steyr M1912 Pistol. The bullet was designed and developed in 1911 but was adopted in 1912 in service by the Austro-Hungarian Army. It was their most used cartridge in World War I. Austria, Romania, and Chile kept using the .9mm Steyr Ammo between the World Wars because of its consistent results and deliverance. The performance of the .9mm Steyr Ammo is quite similar to the .38 ACP Ammo in terms of accuracy, usage, and power, but the .9mm Steyr Ammo has headspaces on the mouth of the case, which creates a slight difference in the comparison. The 115-grain bullet variant of the .9mm Steyr Ammo can travel at a velocity of 1,230 feet per second while creating an energy level of 388 ft.lbf.
The .9mm Steyr Ammo was designed and introduced in 1911 by Styer Arms for the Austria-Hungarian Army. Although, the cartridge was adopted into the service in 1912.
The .9mm Steyr Ammo proved to be a good choice for military purposes and has been widely used by many participants of the World Wars.