Leftism is the debut studio album by English electronic music duo Leftfield, released in 1995 on Columbia Records. It contained a mixture of new tracks along with reworked versions of previous Leftfield singles. The album contains guest spots from musicians not associated with dance music at the time such as John Lydon from Public Image Ltd. and Toni Halliday from Curve. The album was described as progressive house, although some journalists found that label too limiting, suggesting the album incorporated many genres. After completing the album, the duo initially were not pleased with it.

Leftfield are a British electronic music group formed in 1989, a duo of Neil Barnes and Paul Daley. The duo was influential in the evolution of electronic music in the 1990s, with Mixmag describing them as "the single most influential production team working in British dance music". As with many of their contemporaries, such as The Chemical Brothers and Fatboy Slim, Leftfield are notable for their use of guest vocalists in their works. Among them are Toni Halliday on "Original", Johnny Rotten on "Open Up", Djum Djum on "Afro-Left", Earl 16 and Cheshire Cat on "Release the Pressure", and Grian Chatten of Fontaines D.C. on "Full Way Round". The term progressive house was coined to define their style, a fusion of house with dub and reggae.