Porcupine Tree are an English rock band formed by musician Steven Wilson in 1987. During an initial career spanning more than twenty years, they earned critical acclaim from critics and fellow musicians, developed a cult following, and became an influence for new artists. The group carved out a career at a certain distance away from mainstream music, being described by publications such as Classic Rock and PopMatters as "the most important band you’d never heard of".

The band began as a solo project for Wilson, who initially created all of the band's music himself. By late 1993, however, he wanted to work in a band environment, bringing on frequent collaborators Richard Barbieri as keyboardist, Colin Edwin as bassist, and Chris Maitland as drummer to form the first permanent lineup. With Wilson as lead vocalist and guitarist, this remained the lineup until February 2002, when Maitland left the band and Gavin Harrison was recruited to replace him. Porcupine Tree's early sound evoked various styles of psychedelic rock, space rock and experimental rock, later moving towards a more progressive/space rock direction comparable to that of Pink Floyd. Upon signing with Kscope record label in the late 1990s, the band began to approach a more mainstream alternative rock sound. By the early 2000s, the band had signed to a major record label and shifted their sound again, this time in a more progressive metal direction.

In 2010, after the tour in support of their 2009 studio album The Incident, the band became publicly inactive as Wilson committed himself to his solo work and other members began working on their own separate projects. However, Wilson, Barbieri and Harrison continued to intermittently work on material in secrecy over the course of the following decade, leading to the release of their album Closure/Continuation on 24 June 2022.

The band has released 11 studio albums: