This Is Spinal Tap (stylized as This Is Spın̈al Tap: A Rockumentary by Martin Di Bergi) is a 1984 American comedy mockumentary film directed and co-written by Rob Reiner. It stars Christopher Guest, Michael McKean, and Harry Shearer as members of the fictional English heavy metal band Spinal Tap (who are characterized as "one of England's loudest bands"), and Reiner as Martin "Marty" Di Bergi, a documentary filmmaker who follows them on their American tour. The film satirizes the behavior and musical pretensions of rock bands and the hagiographic tendencies of rock documentaries such as Gimme Shelter (1970), The Song Remains the Same (1976), and The Last Waltz (1978). Most of its dialogue was improvised and dozens of hours were filmed.
This Is Spinal Tap received positive reviews, but was only a modest success upon its initial release. However, it found greater success and amassed a cult following after it was released on VHS. In 2002, it was deemed "culturally, historically, or aesthetically significant" by the Library of Congress, and was selected for preservation by the National Film Registry. In 2016, film critic and author Jeremy Arnold chose it as one of the "52 Must-See Movies", describing it as "one of the single most influential movies of the past thirty-five years" and arguing that it "effectively launched a new genre—the mockumentary".