Ozzy Osbourne was an English heavy metal vocalist from Aston, Birmingham. After he was fired from Black Sabbath early in 1979, Osbourne formed a solo band (initially known as Blizzard of Ozz) in November of that year with guitarist Randy Rhoads, bassist Bob Daisley and drummer Lee Kerslake. Since its inception, the group's personnel have changed frequently. The final lineup included guitarist Zakk Wylde (who first joined in 1987 until 1992, spent a second tenure in the band from 2001 and 2009, and then rejoined in 2017), bassist Mike Inez (who first joined in 1989 until 1992, had touring tenures in 1996 and 1998, and returned in 2025), keyboardist and rhythm guitarist Adam Wakeman (who first joined as a touring musician in 2004, and was made an official member with the release of Scream in 2010), and drummer Tommy Clufetos (since 2010).

Until 2020 Osbourne's current touring band always performed on the albums. From Ordinary Man onwards his albums instead featured an array of session and guest musicians with minimal or no contributions from his touring band.

Ozzy Osbourne was fired from Black Sabbath on 27 April 1979, primarily due to his problems with alcohol and drug abuse. The vocalist subsequently rehearsed with a range of musicians in an attempt to form his own band, including guitarists Gary Moore of Thin Lizzy and George Lynch of Dokken, bassist Dana Strum, and drummers Dixie Lee of Lone Star and Dave Potts of Praying Mantis. By November 1979, he had settled on a supergroup lineup including former Quiet Riot guitarist Randy Rhoads, former Rainbow bassist and backing vocalist Bob Daisley, and former Uriah Heep drummer Lee Kerslake.

The new band released their debut album Blizzard of Ozz in September 1980, which also featured keyboard contributions from Don Airey. For the album's promotional tour, this role was handled by Lindsay Bridgwater. After the recording of Diary of a Madman, on which Johnny Cook performed uncredited keyboards, both Daisley and Kerslake were fired; Osbourne has blamed the pair's dismissal on creative differences, while his wife Sharon has cited financial disputes. They were replaced by Rudy Sarzo (a former member of Quiet Riot with Rhoads) and Tommy Aldridge, respectively, who were both credited on the Diary of a Madman album sleeve, despite having not performed on it. After the end of the Blizzard of Ozz touring cycle, Diary of a Madman was released in November 1981.

The Diary of a Madman Tour commenced in December, with Don Airey in place of Bridgwater on keyboards. On 19 March 1982, however, the tour came to an abrupt halt when Rhoads was killed in a plane crash in Leesburg, Florida. The incident occurred when tour bus driver Andrew Aycock took the aircraft out for a joyride and repeatedly flew close to the bus, eventually clipping it and crashing into a building. After a two-week break, Sarzo's brother Robert was chosen as the replacement for Rhoads, although Osbourne's label Jet Records had already promised the position to Bernie Tormé, who joined thereafter.

Tormé debuted with the band on 1 April 1982 in Bethlehem, Pennsylvania. However, after just seven shows he had left again, in part to focus on his solo career but also due to the "horrible ... bad atmosphere" that was present in the wake of Rhoads's death. On 13 April, Night Ranger guitarist Brad Gillis took over from Tormé, remaining for the rest of the tour. Osbourne was contractually obliged by CBS Records to produce a live album before the end of the year, which came in the form of Speak of the Devil, a collection of Black Sabbath covers. After the tour's conclusion in September, Sarzo left Osbourne's band.

For the first leg of the Speak of the Devil Tour in December 1982, Osbourne and his band performed with UFO bassist Pete Way. After Gillis left to return to Night Ranger, the position of guitarist was filled at the end of the year by Jake E. Lee, formerly of Ratt and Rough Cutt. George Lynch, who had previously auditioned for the band in 1979, was initially given the role by Osbourne, but was then immediately fired when Lee was brought in. Don Costa took over from Way for the remainder of the tour, before Bob Daisley returned in time to perform at the US Festival in May. After the recording of Bark at the Moon, Tommy Aldridge was replaced by Carmine Appice, although by early 1984 he had returned due to personal differences and tensions between Osbourne and the new drummer. By the time the Bark at the Moon Tour had finished in January 1985, Aldridge had decided to leave the band again, having not fully enjoyed the role since Rhoads's death.

Lee and Daisley commenced work on the next Ozzy Osbourne album The Ultimate Sin without the eponymous vocalist, who had been admitted to a drug and alcohol rehabilitation centre. Drums were handled initially by Fred Coury and later Jimmy DeGrasso, however the sessions were later scrapped and both Daisley and DeGrasso left the group. By the time recording restarted in the summer, the group consisted of Osbourne, Lee, bassist Phil Soussan and former Lita Ford drummer Randy Castillo. Keyboards on the album were performed by Mike Moran. For the subsequent promotional tour, John Sinclair took over as the band's backup keyboardist.