'Paranoid' was the seminal sophomore studio album by Black Sabbath. First released in September 1970, it was the band's first LP to top the UK Albums Chart, and is often regarded as one of the most quintessential and influential albums in heavy metal history.

'Paranoid' contains several of the band's signature songs, including "Iron Man," "War Pigs" and the title track, which was the band's only Top 20 hit, reaching number 4 in the UK charts.

Black Sabbath returned to the studio with producer Roger Bain in June 1970, just four months after their debut album was released. 'Paranoid' crystallized the band's writing process, with Iommi initiating the ideas with his charred riffs, Ozzy (Osbourne) working on a melody, Geezer providing drive and the majority of the lyrics, and Bill Ward locking into a set of often pounding rhythms beneath Butler's bass rumble. Most of the songs on 'Paranoid' evolved during onstage improvisational jams.

'Paranoid's chart success allowed the band to tour the US for the first time in October 1970, which spawned the release of the album's second single "Iron Man."

As of 2014, 'Paranoid' is Black Sabbath's best-selling album, having sold 1.6 million copies in the US since the beginning of the SoundScan era.