Lightbulb Sun is the sixth studio album by British progressive rock band Porcupine Tree, first released in May 2000. There are four editions: the original release on Snapper records, a German 2-disc tour release on Snapper, with a blue flame on the cover instead of the original orange, an Israeli 2-disc edition on Helicon Records, and the 2- and 3-disc CD/DVD-A reissue on Kscope, in which cover artwork the orange flame has been turned to red. Classic Rock magazine described the album as "an album of stunning songs and startling musicianship… breathtaking."

The album is divided into two parts by a half-minute gap between "Rest Will Flow" and "Hatesong". The first part concentrates more on melodic, pop elements of Porcupine Tree's style, while the second has a more experimental character.

A CD/DVD-A remaster with 5.1 Surround Sound and a new stereo mix was released on April 7 2008 from the Porcupine Tree store. Pre-orders of the Porcupine Tree store edition came with an exclusive 2 track bonus CD containing the tracks; "Novak" and "Buying New Soul (Instrumental Backing Track)". The CD/DVD-A album reissue was released for a mass market on April 21 2008 through the Kscope label at Christchurch Studios, Clifton, Bristol in January 2000, recorded by John Waterhouse.