Green Day is an American punk rock band formed in 1987 by lead vocalist and guitarist Billie Joe Armstrong and bassist and backing vocalist Mike Dirnt. For much of their career the band has been a trio with drummer Tré Cool. In 2012 guitarist and backing vocalist Jason White became a full member after playing in the band as a session and touring guitarist for 13 years. Cool replaced former drummer John Kiffmeyer in 1990, prior to the recording of the band's second studio album, Kerplunk (1992).

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 from the independent record label Lookout! Records. In 1994, its major label debut Dookie released through Reprise Records became a breakout success and eventually sold over 10 million copies in the U.S. Green Day was widely credited, alongside fellow California punk bands Sublime, Bad Religion, the Offspring, and Rancid, with popularizing and reviving mainstream interest in punk rock in the United States.