"The Number of the Beast" is Iron Maiden's seventh single and the second single from Iron Maiden's 1982 album of the same name. The song is inspired by both a nightmare bandleader and bassist Steve Harris had after watching the movie Damien: Omen II, and the storyline of the poem Tam o' Shanter. "The Number of The Beast" is one of Iron Maiden's greatest hits, and is almost always performed during concert. It reached 18 in the UK charts. The track is known for its very long, high-pitched and guttural scream by Bruce Dickinson at the end of the intro. In the documentary on the album of the same name, as part of the Classic Albums series by the BBC, Dickinson said this was due to producer Martin Birch forcing Bruce to sing the first four lines for several hours, over and over again. The frustration of this culminated in this scream, the pitch of which Dickinson has not managed to re-create live since the early days, which may possibly be an influence to the using of the death growl singing technique of later death metal and groove metal vocalists.

The song is about a man who is wandering alone and happens upon a portion of Hell on Earth, with people performing Satanic rituals and sacrifices. At first, he is disgusted and decides to report it to law enforcement, but eventually becomes entranced by the ordeal and decides to join in.

The single's cover is the last of three singles to feature Riggs' depiction of Satan, which debuted on the cover of the Purgatory single. The cover of The Number of the Beast is the aftermath to the cover of the Run to the Hills single where Eddie and Satan are depicted in battle.

The band had asked the famous horror films actor Vincent Price to read the intro text. However, according to Bruce, Price refused to do it for anything less than £25,000. They had heard of someone who read ghost stories at the Capitol radio station and got him to do it. The man was a theatre actor who had no interest in Maiden, but they asked him to put on a Vincent Price kind of voice.

The original music video featured the band performing the song, interspersed with clips from various horror films including Godzilla. The Crimson Ghost - used as a logo by The Misfits - also appears early in the video, and there is another reference to The Misfits later in the video, when the monster from The Angry Red Planet appears (The Misfits used the monster on the cover of their album Walk Among Us). In the middle of the guitar solo, a dancing couple wearing cards marked "6" on their costumes appear on stage. As the male dancer spins his female partner around, her face turns into a wolf-like appearance before they dance out of the stage. Eddie also makes an appearance towards the end of the video. A later video (available on the Visions of the Beast DVD), animated by Camp Chaos, replaced the film clips and the dancing couple with Flash animation of Bruce (acting as a priest) and Eddie re-enacting scenes from The Exorcist.

The original B-side "Remember Tomorrow (Live)" was repeatedly claimed by the band to have been recorded back in 1981 in Milan, Italy during Bruce's warm-up gigs. However, this was found to be untrue when fans discovered it to be the same recording from "Remember Tomorrow" as recorded live by the band with Paul Di'Anno for the live EP, Maiden Japan, with Bruce Dickinson's vocals overdubbed onto the track.

The song made it in at #7 on VH1's 40 Greatest Metal Songs .

"The Number of the Beast" was ranked #6 in Martin Popoff's 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. .

In January 2005, a new and updated version was released. It features live video renditions of "Number of the Beast" and "Hallowed Be Thy Name" that have never been officially released before.

It has since been covered by Iced Earth, Saints in Hell, Avulsed, Breed 77, Sinergy, Powderfinger, Zwan (whose version was used for the soundtrack of the cult film Spun), The Iron Maidens and many other bands. The song is also featured on The String Quartet Tribute to Iron Maiden.

This song was featured on the video game Tony Hawk's Pro Skater 4 and is playable in Guitar Hero III: Legends of Rock as a master track. It is also available in Rock Band as a downloadable song, albeit a cover version.