Blur 21 is a CD, DVD and vinyl box set encompassing the vast majority of music by Blur. It was released on 30 July 2012, commemorating the 21st anniversary of the release of Leisure, the band's first album. The release took place before the band's performance at Hyde Park as part of the 2012 Summer Olympics closing ceremony. One version of the box-set consists of eighteen CDs, three DVDs, one vinyl 7" record and a hardcover book acting as a complete biography of the band. The CDs contain all seven Blur albums, with the first five remastered, with each album receiving a new second disc of B-side material; as well as four 'rarities' discs containing mostly previously unreleased material. The DVDs contain Showtime, The Singles Night and an all-new rarities disc. It is the band's most complete retrospective release.

Blur were an English rock band formed in London in 1988. The band consists of singer Damon Albarn, guitarist Graham Coxon, bass guitarist Alex James and drummer Dave Rowntree. Their debut album, Leisure (1991), incorporated the sounds of Madchester and shoegaze. Following a stylistic change influenced by English guitar pop groups such as the Kinks, the Beatles and XTC, Blur released the albums Modern Life Is Rubbish (1993), Parklife (1994) and The Great Escape (1995). As a result, the band helped to popularise the Britpop genre and achieved mass popularity in the UK, aided by a widely publicised chart battle with rival band Oasis in 1995 dubbed "The Battle of Britpop".