Def Leppard are an English rock band formed in Sheffield in 1977. Since 1992, the band has consisted of Rick Savage (bass, backing vocals), Joe Elliott (lead vocals), Rick Allen (drums), Phil Collen (guitar, backing vocals), and Vivian Campbell (guitar, backing vocals). They established themselves as part of the new wave of British heavy metal of the early 1980s.

The band's first album, 1980's On Through the Night, reached the Top 15 in the UK but received little notice elsewhere. Their second album, 1981's High 'n' Dry, was produced by Mutt Lange, who helped them to define their melodic hard rock style. The album's most popular track, "Bringin' On the Heartbreak", became one of the first rock videos played on MTV in 1982. Their next studio album, Pyromania, the first with Collen replacing guitarist Pete Willis, was released in January 1983, with "Photograph" and "Rock of Ages" both topping the US Rock Tracks chart and reaching the top 20 of the Hot 100. Reaching No. 2 on the US album chart, Pyromania was certified Diamond in the US. The band's fourth album, the more pop-oriented Hysteria (1987), topped the UK, US, Canadian and Australian charts and remained on the charts for over two years. It has sold over 15 million copies worldwide, making it one of the best-selling albums of all time. Hysteria spawned six Top 20 US singles: The US Billboard Hot 100 No. 1 "Love Bites", "Pour Some Sugar on Me" (US No. 2), "Hysteria", "Armageddon It" (US No. 3), "Animal" (at No. 6, the biggest UK hit), and "Rocket".

Following the death of guitarist Steve Clark in 1991, the band recorded their next studio album, Adrenalize (1992), as a four-piece before adding Campbell for the subsequent tour. The album reached No. 1 on the UK, US and Australian charts. It contained several hits, including the Billboard chart-topper "Let's Get Rocked". The album's third single, "Have You Ever Needed Someone So Bad", was a Top 10 song in the US, UK and Canada. Adrenalize went on to sell over eight million copies worldwide. The band's 1993 album, Retro Active, contained the acoustic Top 5 hit "Two Steps Behind". Their greatest-hits album, Vault (1995), featured the UK No. 2 hit "When Love & Hate Collide" and reached the Top 10 in several countries.

As one of the world's best-selling music artists, Def Leppard have sold more than 100 million records worldwide. They have received RIAA diamond certification for two albums, Pyromania and Hysteria, making them one of only five rock bands with two original studio albums that have sold more than 10 million copies in the US. Def Leppard were ranked No. 31 in VH1's "100 Greatest Artists of Hard Rock" and No. 70 in "100 Greatest Artists of All Time". They were inducted into the Rock and Roll Hall of Fame in 2019.