Michael Ryan Pritchard (born May 4, 1972), known professionally as Mike Dirnt, is an American musician best known for being the bassist, backing and occasional lead vocalist, and co-founder of the American punk rock band Green Day. He has also played in several other bands, including The Frustrators. His stage name was originally a nickname from his friends at grade school, as he would constantly play "air bass" and make a "dirnt, dirnt, dirnt" noise while pretending to pluck the strings.