"Paranoid" is a song by Black Sabbath that appears on the band's breakthrough album Paranoid. Supposedly, the members of Black Sabbath put together this song in 15 minutes based on a solo by Tony Iommi. This song was only meant to be a "filler", but became one of Black Sabbath's most well known songs. The record company changed the album's name from War Pigs, as it was originally intended, to Paranoid out of fear of a backlash from supporters of the Vietnam War.

"Paranoid" is uncharacteristically fast and simple for a Black Sabbath song, and is one of the most-covered songs of all time. Unlike most of the band's songs, "Paranoid" was short enough (just under 3 minutes) to be released as a single, as well as to receive airplay on mainstream radio. The single, with "The Wizard " on the B-side, was released in the UK in July 1970 and it reached the number 4.

Lead singer Ozzy Osbourne has continued to play this song as a solo artist and did a version live with Randy Rhoads, which was released on the live album Tribute and the complition album The Essential Ozzy Osbourne.

"Paranoid" was ranked #34 on VH1's 40 Greatest Metal Songs . In March 2005, Q magazine placed it at number 11 in its list of the 100 Greatest Guitar Tracks. Rolling Stone ranked it #250 on their list of the 500 Greatest Songs of All Time.

Paranoid was ranked #1 in Martin Popoff book "The Top 500 Heavy Metal Songs Of All Time". Popoff put together this book by requesting thousands of metal fans, musicians, and journalists to send in their favourite heavy metal songs. Almost 18,000 individual votes were tallied and entered into a database from which the final rankings were derived. .