Black Flag is an American punk rock band formed in 1976 in Hermosa Beach, California. Initially called Panic, the band was established by Greg Ginn, the guitarist, primary songwriter, and sole continuous member through multiple personnel changes in the band. They are widely considered to be one of the first hardcore punk bands, as well as one of the pioneers of post-hardcore.

Through numerous name changes, breakups, and stylistic differences, Black Flag reformed in 2003, broke up, and reformed once more in 2013. After releasing one album (What The…), they broke up again only to reform as recent as 2019.

The band has become a symbol for anarchism and the do-it-yourself ethic, influencing several famous bands including Nirvana.