Diary of a Madman is the second studio album by British heavy metal vocalist Ozzy Osbourne. It was released on 7 November 1981, and re-issued on CD on 22 August 1995. This is the last Osbourne studio album to feature guitarist Randy Rhoads and drummer Lee Kerslake. An altered version appeared in 2002 with the original bass and drum parts removed and re-recorded. In 2011, a Deluxe 30th Anniversary Edition was released with all original parts restored. To date, the album has sold over 3 million copies worldwide.
 
Reception of the album has been generally positive. In particular, the neo-classical guitar work of Randy Rhoads has received much praise. Steve Huey of AllMusic stated that "it's not uncommon to find fans who prefer Diary to Blizzard, since it sets an even more mystical, eerie mood, and since Rhoads' playing is progressing to an even higher level". BBC Music referred to the album as "a classic rock record in every way", "lifted out of the ordinary by the legendary rock axe god, Randy Rhoads". Canadian journalist Martin Popoff called Diary of a Madman "a lasting classic that stands as the definitive showcase for Randy Rhoads."
Though the album is regarded quite favorably today, reviews upon its 1981 release were often less than enthusiastic. J. D. Considine of Rolling Stone, for example, opined upon the album's original release that "the songs here are little more than riffs with a vocal line pasted on top" and referred to Rhoads as "a junior-league Eddie Van Halen – bustling with chops but somewhat short on imagination". The magazine, however, would change its tune and later rank the album 15th on its 2017 list of "100 Greatest Metal Albums of All Time".