Diary of a Madman is an album by Ozzy Osbourne. It was released on November 7, 1981, and re-issued on August 22, 1995. An altered version appeared in 2002. This is the last album with Randy Rhoads before his untimely death in 1982. Although bassist Rudy Sarzo and drummer Tommy Aldridge are credited in the liner notes and pictured on the inner sleeve, it was bassist Bob Daisley and drummer Lee Kerslake who performed all bass and drum parts on the original release. They were not given credit for their contributions. According to a 2005 interview with Daisley, even though Don Airey is credited for having played keyboards on this record, it was in fact a musician named Johnny Cook who recorded the keyboard parts, as Airey was unavailable at the time. The album features several songs with acoustic intros, including "You Can't Kill Rock and Roll", "S.A.T.O.", "Tonight", and the title track.

The RIAA certified Diary of a Madman Gold (500,000 units sold) on January 04 1982, Platinum (1 million units sold) on May 10 1982, Multi-platinum (2) (2 million units, known unofficially as Double Platinum) on August 11 1992 and MP (3) (3 million units, known unofficially as Triple Platinum) on October 26 1994.