Billie Joe Armstrong (born February 17, 1972) is an American singer-songwriter, musician, guitarist, multi-instrumentalist, and actor. He is best known as the lead vocalist, principal songwriter, and guitarist of the punk rock band Green Day, which Armstrong co-founded with Mike Dirnt. He is also a guitarist and vocalist for the punk rock band Pinhead Gunpowder and provides lead vocals for Green Day's side projects Foxboro Hot Tubs and The Network.

Raised in Rodeo, California, Armstrong developed an interest in music at a young age, and recorded his first song at the age of five. He met Mike Dirnt while attending elementary school, and the two instantly bonded over their mutual interest in music, forming the band Sweet Children when the two were 15 years old. The band changed its name to Green Day, and would later achieve massive commercial success. Armstrong has also pursued musical projects outside of Green Day's work, including numerous collaborations with other musicians.