G.I.S.M. (ギズム, Gizumu) is a Japanese hardcore punk band formed in Tokyo in 1981. Even though the guitar style resembled heavy metal in many aspects, GISM was one of the first Japanese hardcore bands, while at the same time drawing influence from the early industrial/avant-garde music scene—something uncommon in punk bands at that time. The acronym GISM has many different variations; they include: "Guerrilla Incendiary Sabotage Mutineer" (original), "God In the Schizoid Mind", "Grand Imperialism Social Murder", "Genocide Infanticide Suicide Menticide", "Gay Individual Social Mean", "Gothic Incest Sex Machine", "Grubby Incest Stripper Mastitis", "Gravity Impel Slaying Machine", "Get Incinerated Sorrow Mass", "Gore Impromptu Suicide Mine", "Grim Iconic Sadistic Mantra" and "Gnostic Idiosyncrasy Sonic Militant".
GISM has attained a cult status in the international punk scene, duly for their unique blend of heavy metal and hardcore punk. Roadrunner Records ranked Sakevi Yokoyama No. 49 out of 50 of The Greatest Metal Frontmen of All Time.