Black Sabbath was an English rock band formed in Birmingham in 1968 by Tony Iommi, Bill Ward, Geezer Butler, and Ozzy Osbourne. Pioneers of heavy metal, they were known for their dark, occult themes and heavy, down-tuned guitar sound. Their early albums, including Black Sabbath, Paranoid, and Master of Reality, are widely regarded as genre-defining classics. Over the years, the band underwent numerous lineup changes, featuring notable members such as Ronnie James Dio and Ian Gillan. Despite constant personnel shifts, Black Sabbath continued to release influential albums and explore new musical directions. The original lineup reunited several times, most notably in the late 1990s and for a final tour in 2017. Black Sabbath is frequently cited alongside Led Zeppelin and Deep Purple as one of the most significant British hard rock bands of the seventies. With over 70 million records sold, a place in both the UK Music and Rock and Roll Halls of Fame, and multiple Grammy Awards, Black Sabbath remains one of the most influential bands in rock history.