Black Sabbath vocalist Ozzy Osbourne has always spoken fondly of the recording of the band's debut album, stating in his autobiography , "Once we'd finished, we spent a couple of hours double-tracking some of the guitar and vocals, and that was that. Done. We were in the pub in time for last orders. It can't have taken any longer than twelve hours in total. That's how albums should be made, in my opinion." Drummer  agrees, telling  in 2001, "I think the first album is just absolutely incredible. It's naïve, and there's an absolute sense of unity – it's not contrived in any way, shape or form. We weren't old enough to be clever. I love it all, including the mistakes!" In an interview for the  series in 2010 Butler added, "It was literally live in the studio. I mean, (producer) , I think he's a genius the way he captured the band in such a short time."

's Steve Huey feels that Black Sabbath marks "the birth of  as we now know it". In his opinion, the album "transcends its clear roots in  and  to become something more". He ascribes its "sonic ugliness" as a reflection of "the bleak industrial nightmare" of the group's hometown, , England. Huey notes the first side's allusions to themes characteristic of heavy metal, including evil, , and , "as filtered through horror films and the writings of , , and ." He characterises side two as "given over to loose blues-rock jamming learned through" the English rock band .

In the opinion of the author and former  magazine editor Jeff Wagner, Black Sabbath is the "generally accepted starting point" when heavy metal "became distinct from ". In his opinion, the album transfigured blues rock into "something uglier, found deeper gravity via mournful singing and a sinister rhythmic pulse". According to  magazine, "the album that arguably invented heavy metal was built on thunderous ". 's Mike Stagno notes that Black Sabbath's combined elements of ,  and , with heavy  created one of the most influential albums in the history of heavy metal. In retrospect, Black Sabbath has been lauded as perhaps the first true heavy metal album. It has also been credited as the first record in the  and  genres.

Taking a broader perspective,  of  says, "The debut Black Sabbath album of 1970 was a watershed moment in heavy rock, but it was part of a larger trend of artists, producers, and engineers already moving towards the sound we now call hard rock and heavy metal.

Track listing

All songs credited to , ,  and , except where noted.

Side oneNo.TitleLength1."Black Sabbath"6:202."The Wizard"4:223."Wasp / Behind the Wall of Sleep / Bassically / N.I.B."9:44Side twoNo.TitleWriter(s)Length4."Wicked World" 4:475."A Bit of Finger / Sleeping Village / Warning" Iommi Butler Ward Osbourne / Dunbar Dmochowski Hickling Moorshead 14:15