The 9mm Mak or 9×18mm Makarov is a Soviet pistol and submachine gun cartridge. During the latter half of the 20th century it was a standard military pistol cartridge of the Soviet Union and the Eastern Bloc, analogous to the 9×19mm Parabellum in NATO and Western military use.
The 9×18mm Makarov is ballistically inferior to the 9×19mm Parabellum cartridge. While there are no official SAAMI pressure specifications for the 9×18mm Makarov cartridge, tests indicate that surplus ammunition develop pressures in the mid 20,000 psi, significantly less than the 35,000 psi or more generated by 9×19mm Parabellum (+P) loads. As such it is designed to be used in low-powered blowback semiautomatics, much like the .380 ACP cartridge, rather than locked-breech designs encountered, but not always required, for higher pressure cartridges like the 9×19mm Parabellum.