Rancid is an American punk rock band formed in Berkeley, California, in 1991. Founded by Tim Armstrong and Matt Freeman, former members of the band Operation Ivy, Rancid is often credited (alongside Green Day and the Offspring) as being among the wave of bands that revived mainstream interest in punk rock in the United States during the mid-1990s. Over its 34-year career, Rancid has retained much of its original fan-base, most of which was connected to its underground musical roots.

Rancid has had two lineup changes since its inception, with Tim Armstrong and Matt Freeman being continuous members. Their current lineup consists of Armstrong on guitar and vocals, Freeman on bass and vocals, Lars Frederiksen on guitar and vocals, and Branden Steineckert on drums. The band was formed by Armstrong, Freeman, and former drummer Brett Reed, who left the band in 2006 and was replaced by Steineckert. This lineup recorded their first album, with Frederiksen joining the band on their subsequent tour.

To date, Rancid has released ten studio albums, one split album, one compilation, two extended plays, and a series of live online-only albums, and has been featured on a number of compilation albums. The band has sold over four million records worldwide, making it one of the most successful punk rock groups of all time. The band rose to popularity in 1994 with its second studio album, Let's Go, featuring the single "Salvation". In the following year, Rancid released its highly successful album ...And Out Come the Wolves, which produced its best-known songs "Roots Radicals", "Ruby Soho", and "Time Bomb", and was certified gold and platinum by the RIAA, selling over one million copies in the United States alone. Its next six albums – Life Won't Wait (1998), Rancid (2000), Indestructible (2003), Let the Dominoes Fall (2009), ...Honor Is All We Know (2014) and Trouble Maker (2017) – were also critically acclaimed, though not as commercially successful as ...And Out Come the Wolves. The band released their tenth album, Tomorrow Never Comes, in 2023.

Childhood friends Tim Armstrong and Matt Freeman grew up together in Albany, California, a small, then–working-class community near Berkeley. The two had been playing together in the influential ska punk band Operation Ivy from 1987 to 1989. The band became popular in the punk scene at 924 Gilman Street, a club and concert venue featuring Bay Area punk bands. When Operation Ivy broke up, Armstrong and Freeman decided to form a new band, and formed a ska punk band called Downfall, which disbanded after a few months. They then started a hardcore punk band called Generator, which also disbanded shortly after. They also started the ska influenced Dance Hall Crashers, though they left the band shortly after it was formed. During this time, Armstrong was struggling with alcoholism, and to keep him focused on other interests, Freeman suggested they form a new band. In 1991, they recruited Armstrong's roommate Brett Reed as their drummer and formed Rancid.

A few months after the band's inception, Rancid began performing around the Berkeley area, and quickly developed a fan following. Rancid's first recorded release was a 1992 EP for Operation Ivy's old label Lookout! Records. Shortly after releasing the extended play, the band left Lookout! and was signed to Bad Religion guitarist Brett Gurewitz's record label, Epitaph Records. Rancid released its self-titled debut album through Epitaph in 1993.

While Rancid was writing for a follow-up album, Billie Joe Armstrong joined them to co-write the song "Radio", which resulted in Armstrong playing a live performance with Rancid. Tim had previously asked Lars Frederiksen to be Rancid's second guitarist, but he turned down the request initially as he was playing with the UK Subs at the time. After Billie Joe turned down the request, Frederiksen changed his mind and joined Rancid.

Frederiksen played with the band on its second studio album Let's Go (1994). That year, its then-label-mates, the Offspring, experienced huge success with its album Smash. Rancid supported the Offspring's 1994 tour, which helped Let's Go reach number 97 on Billboard's Heatseekers and the Billboard 200 charts, respectively. The album also provided its first widespread exposure when MTV broadcast the video for the single "Salvation". Let's Go was certified gold on July 7, 2000, and with the success of the album, the band was pursued by a number of major record labels, including Madonna's label Maverick Records. Many rumors circulated during this time period. Some of the rumors were Epitaph employees were not allowed to discuss matters with the press, Rancid convinced an A&R man from Epic to shave a blue mohawk, and Madonna sent the band nude pictures of herself.

The band eventually decided to remain signed to Epitaph, and the next year released its third album ...And Out Come the Wolves on August 22, 1995. The album quickly surpassed Let's Go in terms of success, and reached number 45 on the Billboard 200 album chart. on January 22, 1996, the album was certified gold. and in 2004 it was certified platinum. The album received positive reviews, Stephen Thomas Erlewine of AllMusic described the album as having "classic moments of revivalist punk". Erlewine praised the music and claims the album "doesn't mark an isolationist retreat into didactic, defiantly underground punk rock". Three of the album's singles, "Roots Radicals", "Time Bomb", and "Ruby Soho" all charted on the Billboard Modern Rock Tracks, and earned Rancid its heaviest airplay on MTV and radio stations to date. The band also performed "Roots Radicals" and "Ruby Soho" on Saturday Night Live. They also performed as a mainstage act on that years Lollapalooza tour.