Helloween is a German power metal band founded in 1984 in Hamburg by members of bands Iron Fist, Gentry, Second Hell and Powerfool. Its first lineup consisted of singer and guitarist Kai Hansen, bassist Markus Grosskopf, guitarist Michael Weikath and drummer Ingo Schwichtenberg. By the time Hansen quit Helloween in 1989 to form Gamma Ray, the band had evolved into a five-piece, with Michael Kiske taking over as lead vocalist. Schwichtenberg and Kiske both parted ways with Helloween in 1993; Schwichtenberg died two years later as the result of suicide. Between then and 2016, there had been numerous line-up changes, leaving Grosskopf and Weikath as the only remaining original members. As a septet, their current lineup includes four-fifths of the Keeper of the Seven Keys: Parts I and II-era (1987–1988) lineup, featuring three additional members, vocalist Andi Deris (who had replaced Kiske in 1994), guitarist Sascha Gerstner and drummer Daniel Löble.
Since its inception, Helloween has released 16 studio albums, three live albums, three EPs and 30 singles, was honored with 14 gold and six platinum awards and has sold more than ten million records worldwide. Helloween has been referred to as the "fathers of power metal", as well as one of the so-called "big four" of the genre's early German scene, along with Grave Digger, Rage and Running Wild, and as one of power metal "big four" overall, along with Blind Guardian, Sabaton and DragonForce.