Pinhead Gunpowder is an American punk rock band that formed in East Bay, California, in 1990. The band has consisted of Aaron Cometbus (drums, lyrics), Bill Schneider (bass), Billie Joe Armstrong (guitar, vocals) and Jason White (guitar, vocals) for the majority of its existence. Sarah Kirsch (guitar, vocals), formerly known as Mike Kirsch, was the original guitarist, in place of White, but left the band citing personal differences with Green Day (the band for which Billie Joe Armstrong is most famous) and their major label debut album Dookie (1994). The band's name comes from a brand of "high octane" green tea served at the Arcata co-op and discovered by Aaron Cometbus during one of his many dumpster diving adventures.

Cometbus, who releases the Cometbus fanzine, has played in many East Bay area bands such as Crimpshrine, Sweet Baby, The Thorns of Life and many more; Schneider is Green Day's former guitar tech and tour manager. Jason White plays additional guitar for Green Day; along with founding the seminal punk rock band Chino Horde. White has played in The Influents as well as The Big Cats. Sarah Kirsch has also been an active member in several East Bay bands such as Fuel, Torches to Rome, Bread and Circuits and many others.

The vast majority of Pinhead Gunpowder's songs were written by Cometbus, although a few songs such as "27", "Anniversary Song" and "New Blood" were written by Billie Joe Armstrong under the pseudonym "Wilhelm Fink".

Pinhead Gunpowder is a very elusive band. Over their 24+ year existence they have only released a few albums and only played 18 shows in total (that are known of). All of these shows have been on the west coast of the USA, mostly in the Bay Area. Their two lead singers are both members of Green Day and because of that the majority of their time is spent recording and touring for Green Day. Founder, drummer, and lyricist Aaron Cometbus is also busy writing his Cometbus zine, several novels, and in 2014 his first volume of poetry as well as producing artwork and playing in numerous bands. As a result of their busy lives Cometbus wrote that they knew upon forming Pinhead Gunpowder that it would have to be a part-time band that they could all come back to when they had free time.