Green Day, an American rock trio, have origins that can be traced back to 1987, when 14 year old friends Billie Joe Armstrong and Mike Dirnt formed a band called Sweet Children, and played their first show in the October of that year at Rod's Hickory Pit in Vallejo, California where Armstrong's mother was working. The following year Armstrong and Dirnt began working with former Isocracy drummer John Kiffmeyer (also known as Al Sobrante), who began to serve as both the drummer and business manager. Larry Livermore, owner of Lookout! Records, saw the band play an early show and signed them to his label. In 1989, the band dropped the name Sweet Children (according to Livermore this was done in order to avoid confusion with another local band Sweet Baby) and adopted the name Green Day, allegedly due to their fondness of marijuana. 1989 also saw the recording of their first EP, “1,000 Hours”. Lookout! went on to release Green Day's first LP, “39/Smooth” in early 1990, and also released 2 EPs later that year, “Slappy” and “Sweet Children”. Shortly after the band's first nationwide tour, Sobrante left the East Bay area to attend college, with The Lookouts drummer Tré Cool filling in as a temporary replacement, however it became clear that Sobrante did not plan on committing to the band full time, and Cool's position became permanent. In 1991, Lookout! released “1,039/Smoothed Out Slappy Hours”, a compilation of the bands 3 releases in 1990.
Second LP “Kerplunk” sold around 50,000 copies in the US (considered quite a large amount for the independent punk scene in 1992), and this success led to increased interest from major record labels. Eventually, the band left Lookout! on friendly terms and signed with Reprise Records after attracting the attention of producer Rob Cavallo, however signing to Reprise caused many punk rock fans to regard Green Day as sellouts.

The band immediately went to work on its major label debut, “Dookie”, recorded in 3 weeks and released in February 1994. Its singles "Longview", "Basket Case", and "When I Come Around" all reached number 1 on the Modern Rock Tracks chart, and “Dookie”won the 1995 Grammy Award for “Best Alternative Album”. It has sold over 10 million copies in the US, and over 15 million worldwide. In 1995, a new single for the “Angus” soundtrack was released, titled "J.A.R.", and it went straight to number 1 on the Billboard Modern Rock Tracks chart. The song was followed by a new album, “Insomniac”, released in late 1995. “Insomniac” uses a piece of art by Winston Smith entitled “God Told Me to Skin You Alive” for its album cover, and although it didn’t match the success of “Dookie”, it still sold 2 million copies in the US (going double platinum) and won the band 1996 American Music Award nominations for “Favorite Artist”, “Favorite Hard Rock Artist”, and “Favorite Alternative Artist”. After that, the band abruptly cancelled a European tour, citing exhaustion.

Green Day began work on a new album in 1997, resulting in “Nimrod”, released in October 1997, entering the charts at number 10, and also going double platinum. 3 years later came “Warning”, but for various reasons a decline in popularity followed, and it was only certified gold. The release of a greatest hits compilation, “International Superhits!”, (which went platinum in the US) and a collection of B-sides, “Shenanigans” (which contained “Espionage” from “Austin Powers: The Spy Who Shagged Me”) followed “Warning”.

In the summer of 2003 the band went into a studio to write and record new material for a new album, tentatively titled “Cigarettes and Valentines”. However, after completing 20 tracks, the master tapes were stolen from the studio – despite being upset, the band chose not to try to re-create the stolen album, and instead started over with a vow to be even better than before. The resulting 2004 LP “American Idiot” debuted at number 1 on the Billboard charts (the band's first ever album to top the chart), won the 2005 Grammy for "Best Rock Album", has sold over 5 million copies in the US, and helped Green Day clean up at the 2005 MTV Music Awards, winning 7 out of the 8 awards they were nominated for. The band toured in support of the album, and filmed and recorded the 2 concerts at the Milton Keynes National Bowl in England, releasing these as a live CD and DVD, “Bullet in a Bible” in November 2005. Green Day won the 2006 Grammy Award for “Record of the Year” for "Boulevard of Broken Dreams" (from “American Idiot”), which spent a then record 16 weeks at number 1 on Billboard's Modern Rock Tracks, a record it shared at the time with Red Hot Chili Peppers' "Scar Tissue" and Staind's "It's Been Awhile" (all these tracks were subsequently beaten by Foo Fighters' 2007 hit "The Pretender" which reigned at the top spot for 18 weeks).

Ever since 1991, the members of Green Day have started and been involved with other projects, such as Billie Joe Armstrong's Pinhead Gunpowder (which also features Green Day's live backup guitarist Jason White) and The Frustrators in which Mike Dirnt plays bass. All 3 members of Green Day play under fake stage names in The Network, and are all in the band Foxboro Hot Tubs (who released an album entitled “Stop, Drop and Roll” in May 2008). In 2003 Green Day collaborated with Iggy Pop on 2 tracks for his album “Skull Ring”. In September 2006, Green Day teamed up with U2 and producer Rick Rubin to record a cover of The Skids song "The Saints Are Coming" to benefit Music Rising, an organization to help raise money for musicians' instruments lost during Hurricane Katrina. Green Day have also released a cover of the John Lennon song "Working Class Hero", featured on the album “Instant Karma: The Amnesty International Campaign to Save Darfur”.

Green Day have sold over 65 million records worldwide, including 22 million in the US.