Geezer Butler, born Terence Butler in Birmingham on 17 July 1949, is being marked on the anniversary of his birth as the bassist and chief lyricist who helped create Black Sabbath and, with it, heavy metal. He named the band, wrote most of its early lyrics, and co-shaped its sound alongside Tony Iommi, Bill Ward and John "Ozzy" Osbourne, work now recognised as foundational to the genre and its many later offshoots.

Butler's path to Black Sabbath ran through several short-lived groups, including the Ruums and The Rare Breed, before he and Osbourne reunited in 1968 in the blues quartet Polka Tulk, which became Earth and then Black Sabbath, borrowing its name from a 1963 horror film. He wrote the band's lyrics for classics such as "Iron Man", "War Pigs" and "Paranoid" until Ronnie James Dio replaced Osbourne in 1979, and later worked outside the band too, touring and recording with Osbourne solo, fronting his own project GZR, and joining Dio-era reunion band Heaven & Hell and supergroup Deadland Ritual. Following Black Sabbath's final show in July 2025 and Ozzy Osbourne's subsequent death, with Iommi and Ward now retired, Butler remains active and has announced he is working on a new solo album.