Sum 41 is a Canadian rock band from Ajax, Ontario, active since 1996. The current members are Deryck Whibley (lead vocals, rhythm guitar), Jason McCaslin (bass guitar, backing vocals), Steve Jocz (drums) and Tom Thacker (lead guitar, backing vocals).

In 1999, the band signed an international record deal with Island Records. The band released their debut album, All Killer No Filler in 2001. The band achieved mainstream success with their first single from the album, "Fat Lip", which reached number-one on the Billboard Modern Rock Tracks chart and remains the band's most successful single to date. All Killer No Filler was certified platinum in the United States, Canada and in the UK. The band has since released three more studio albums: Does This Look Infected? (2002), Chuck (2004) and Underclass Hero (2007). All three albums have been certified platinum in Canada.

The band often performs more than 300 times each year and holds long global tours, most of which last more than a year. They have been nominated for seven Juno Awards and have won twice (Group of the Year in 2002 and Rock Album of the Year for Chuck in 2005). Their fifth studio album, Screaming Bloody Murder, is set for release March 29, 2011.