1,039/Smoothed Out Slappy Hours

1,039/Smoothed Out Slappy Hours is a compilation album comprising early recordings by American rock band Green Day, released October 1, 1991, on Lookout Records. Often erroneously referred to as the band's debut album, the compilation combines the band's actual debut 39/Smooth and its first two EPs Slappy and 1,000 Hours (all currently out of print), as suggested by the amalgamation of the titles of the debut album and two EPs for the resulting compilation album. The album includes one cover, "Knowledge" (originally from the Slappy EP), which was originally by influential California punk band Operation Ivy, whose singer, Jesse Michaels, contributed the artwork for the album. The cover art features the same image from 39/Smooth.

Lookout! re-released the album in 2004 with special limited packaging and all-new enhanced CD-ROM features, including live performances and pictures. The album was re-issued in the same packaging in 2007 through Reprise Records after Green Day pulled the album, along with the remainder of the band's catalog previously released through Lookout!, from the label in August 2005 due to unpaid royalties.

1,039/Smoothed Out Slappy Hours has been certified Gold in the U. S. by the RIAA; according to Nielsen SoundScan, it has sold 632,000 copies in the U. S. as of August 2010. The album was certified Gold in the UK on July 22, 2013, representing sales of at least 100,000 copies. It has sold more than 2 million copies worldwide.