9 mm or 9×19mm Parabellum is a firearms cartridge.
9 mm or 9mm may also refer to:
"9mm" (song), David Banner song 9 mm caliber, cartridges other than 9×19mm with 9 mm bullets 9mm Parabellum Bullet, a Japanese rock band
Rail transport modelling N gauge, 1:160 scale, with rails 9 mm apart, representing standard gauge British N gauge, 1:148 scale, with rails 9 mm apart, representing standard gauge H0e/HOn30 gauge, 1:87.1 scale, with rails 9 mm apart, representing narrow gauge OO9, 1:76 scale, with rails 9 mm apart, representing narrow gauge in Britain Gnine/IIp gauge, 1:22.5 scale, with rails 9 mm apart, representing minimum/miniature gauge