The .38 Super, also known as .38 Super Auto, .38 Super Automatic, .38 Super Automatic +P , .38 Super +P , or 9×23mmSR, is a pistol cartridge that fires a 0.356-inch-diameter (9.04 mm) bullet. It was introduced in the late 1920s as a higher pressure loading of the .38 ACP, also known as .38 Auto. The older .38 ACP cartridge propels a 130-grain (8.4 g) bullet at 1,050 ft/s (320.0 m/s), whereas the .38 Super pushes the same bullet at 1,280 ft/s (390.1 m/s). The .38 Super has gained distinction as the caliber of choice for many top practical shooting competitors; it remains one of the dominant calibers in IPSC competition.

The .38 ACP, also known as the .38 Auto, .38 Automatic, or 9x23mmSR, is a semi-rimmed pistol cartridge that was introduced at the turn of the 20th century for the John Browning-designed Colt M1900. It was first used in Colt's Model 1897 prototype, which he did not produce. The metric designation for the round is 9×23mm SR (semi-rimmed), which is not to be confused with other 9×23mm cartridges.