This is Spın̈al Tap (officially spelled with a non-functional umlaut over the letter 'n' and dotless 'i') is a 1984 mockumentary directed by Rob Reiner and starring members of the semi-fictional heavy-metal/hard rock band Spinal Tap. The film is a mock rockumentary that satirizes the wild personal behavior and musical pretensions of hard-rock and heavy-metal bands.

Much of the film was ad libbed, and several dozen hours of footage were shot before Reiner edited it down to the released film. A 4½ hour bootleg version of the film exists and has been traded among fans and collectors for years.

The three core members of Spinal Tap, David St. Hubbins, Derek Smalls and Nigel Tufnel, are portrayed by the American actors Michael McKean and Harry Shearer and British American Christopher Guest respectively. The three actors actually play their musical instruments and speak credible British English throughout the film. Reiner appears as Marty DiBergi, the maker of the documentary. Other actors in the film are Tony Hendra as the group manager Ian Faith and June Chadwick as St. Hubbin's interfering girlfriend Jeanine. Actors Paul Shaffer, Fred Willard, Fran Drescher, Bruno Kirby, Howard Hesseman, Ed Begley Jr., Patrick Macnee, Anjelica Huston, Dana Carvey and Billy Crystal all play supporting roles or make cameo appearances in the film. Scream queen starlet Brinke Stevens appears in an uncredited cameo as a groupie or girlfriend of a band member.

In 1982 legendary British heavy metal band Spinal Tap attempt an American comeback tour accompanied by a fan who is also a film-maker. The resulting documentary, interspersed with powerful performances of Tap's pivotal music and profound lyrics, candidly follows a rock group heading towards crisis, culminating in the infamous affair of the eighteen-inch-high Stonehenge stage prop. Written by Jeremy Perkins

Marti DeBergi is a film-maker who decides to make a documentary, a rockumentary actually, about the world's loudest band, the British heavy metal group Spinal Tap. The movie is in fact a biting satire and spoof of the whole rock and roll scene that passes itself off as a real documentary of a real band. Hilarious behind-the-scenes footage is combined with faux-concert clips to breath life into the imaginary group. Written by Greg Bole