.357
.357 may refer to:

 .357 Magnum, a firearm cartridge (revolver)
 .357 SIG, a firearm cartridge (pistol)
 .357 Remington Maximum, a wildcat firearm cartridge (revolver)
 .357/44 Bain & Davis, a wildcat firearm cartridge (pistol)
 .357 Peterbilt, a wildcat firearm cartridge (pistol)
 .357 Super Magnum, a wildcat firearm cartridge (revolver)

See also 
 .38 caliber
 9 mm caliber