Green Day is an American punk rock band formed in 1986 by vocalist/guitarist Billie Joe Armstrong and bassist Mike Dirnt. For much of the group's career, the band has been a trio with drummer Tré Cool, who replaced former drummer John Kiffmeyer in 1990 prior to the recording of the band's second studio album, Kerplunk (1992). Guitarist Jason White has performed with the band as a session and touring member since 1999.
Green Day was originally part of the punk scene at the DIY 924 Gilman Street club in Berkeley, California. The band's early releases were with the independent record label Lookout! Records. In 1994, its major label debut Dookie (released through Reprise Records) became a breakout success and eventually shipped over 10 million copies in the U.S.
Green Day was widely credited, alongside fellow California punk bands Sublime, Bad Religion, The Offspring, Blink-182, and Rancid, with popularizing and reviving mainstream interest in punk rock in the United States.
Their sound is often compared to first wave punk rock bands such as the Ramones, The Clash, Sex Pistols, The Jam, and the Buzzcocks. Stylistically, the group is characterized as punk rock, pop punk and alternative rock. Stephen Thomas Erlewine of AllMusic described Green Day as "punk revivalists who recharged the energy of speedy, catchy three-chord punk-pop songs." While Armstrong is the primary songwriter, he looks to the other band members for organizational help.