G.I.S.M. was a Japanese hardcore punk band (with metal leanings) formed in Japan in 1981. It was composed of vocalist Sakevi Yokoyama(real name Shigehisa. "Sakevi" being a corrupted "sakebi" - a shout, or scream of "MURDER!"), guitarist Randy Uchida, bassist Kannon(sometimes known as "Cloudy", later replaced by Kiichi Takahashi in the 90's), and drummer Monamour Hiroshima(replaced by Ironfist Tatsushima around the same time Kannon left). GISM often used heavy metal style guitar solos and riffs, while at the same time drawing much influence from the early industrial/avant-garde music scene...something extremely uncommon in punk bands at that time.

GISM has attained a cult status in the hardcore punk scene, probably due to their violent attitude and bizarre artworks/performances,coupled with the legends surrounding them. Some claimed Sakevi was a yakuza member and that he doesn´t allow any store in Japan to sell or distribute any GISM material (even resorting to violence to prevent this). It was also rumor that Sakevi was mentally ill, a rumor not helped any by his paying a fine for acts of violence offstage.

The acronym GISM has never had a constant meaning attached to it. Variations include God In The Schizoid Mind, Guerilla Incendiary Sabotage Mutineer, General Imperialism Social Murder and Gnostic Idiosyncracy Sonic Militant.