Bad Religion is an American punk rock band, formed in Los Angeles, California, in 1980. The band's lyrics cover topics related to religion, politics, society, the media and science. Musically, they are noted for their melodic sensibilities and extensive use of three-part vocal harmonies. The band has experienced multiple line-up changes, with singer Greg Graffin being the band's only constant member, though fellow founding members Jay Bentley and Brett Gurewitz have also been with the band for most of their history while guitarist Brian Baker has been a member of the group since 1994. Guitarist Mike Dimkich and drummer Jamie Miller have been members of the band since 2013 and 2015 respectively. To date, Bad Religion has released seventeen studio albums, two live albums, three compilation albums, three EPs, and two live DVDs. They are considered to be one of the best-selling punk rock acts of all time, having sold over five million albums worldwide.

After gaining a large underground following and critical praise through their releases on Gurewitz's label Epitaph in the 1980s and early 1990s, Bad Religion experienced mainstream success after signing to the major label Atlantic in 1993. The band pioneered the punk rock revival movement of the 1990s, establishing a formula for California-based punk bands such as Green Day and Epitaph-signed acts the Offspring, NOFX and Rancid. They are also cited as an inspiration or influence on the 1990s and 2000s pop punk, skate punk, post-hardcore, screamo and emo scenes.

Atlantic reissued the previously-released-on-Epitaph album, Recipe for Hate (1993), which became commercially successful, as did its 1994 follow-up Stranger than Fiction. Stranger than Fiction included some of Bad Religion's well-known hits, including "Infected", "Stranger than Fiction", and the re-recorded version of "21st Century (Digital Boy)" (the latter of which its original version appeared four years earlier on Against the Grain); the album was later certified gold in both the United States and Canada. Shortly before the release of Stranger than Fiction, Gurewitz left Bad Religion to run his label Epitaph on a full-time basis, and was replaced by Brian Baker. The band's success had slowly dwindled by the late 1990s, and, after three more albums, they were dropped from Atlantic in 2001; this resulted in Bad Religion returning to Epitaph and Gurewitz rejoining the band. Since then, they have undergone a resurgence in popularity, with "Sorrow", "Los Angeles Is Burning", and "The Devil in Stitches" becoming Top 40 hits on the US charts while their sixteenth studio album, True North (2013), became Bad Religion's first album to crack the top 20 on the Billboard 200 chart where it peaked at number 19. The band's seventeenth and most recent studio album, Age of Unreason, was released on May 3, 2019.