Def Leppard hit the lights in 1977 with Pete Willis (guitar), Rick Savage (bass), Steve Clark (guitar) and Tony Kenning (drums) at the helm. They were originally called Atomic Mass and took the present name when Joe Elliot joined on vocals. Their first gig was at an elementary school in front of 150 children and, shortly after a few more gigs, their drummer was replaced by Frank Noon.
In 1979 their debut EP, on their own 'Bludgeon Riffola Records', was released titled Getcha Rocks Off in 1978; but once again they had drummer problems when Frank Noon returned to his former outfit and was replaced by Rick Allen. When they toured with AC/DC and Sammy Hagar in 1979 they generated interest and were then offered a deal by 'Vertigo Records', and the debut On Through The Night resulted in 1980. They then relocated to London. It was with this that they got their first headline tour and a trip to America. This trip was unpopular with their old school fans that accused them of selling out.
High And Dry (1981), although competent, received little notice. In 1983 Pyromania was released and proved to be their most successful venture to date. During that year it was the second biggest selling album - second only to Michael Jackson's Thriller, especially due to the hit resulting singles Rock of Ages and Photograph. Unfortunately they were unable to take advantage and duplicate this feat. The album was legendary for its use of technology and studio effects that would revolutionize Heavy Metal in the 1980s. Trouble started, however, when Pete Willis was given the push after he showed up drunk for meetings; he was replaced with Phil Collen. They also received flak from die-hard fans that noticed their drifting from their NWOBHM roots into a more Pop-Metal style, a style that would dominate their music for the rest of their career. But their luck didn't change by New Year's 1984, when Rick Allen was in a car accident which caused him to loose his left arm. For most drummers this would spell the end of a career, but not in Def Leppard. The band kept their faith and Allen rehabilitated and learned to use his feet and right arm to do the work, with the help of a specially made drum kit. The incident only held the band back a short while for three top 10 charting singles were released during this period with a #1 for Love Bites. The tragedy delayed the release of Hysteria, their next album, until 1987. The wait was worth it, however, because the album sold 15 million copies and produced two U.S. #5 singles, Armageddon It and Pour Some Sugar On Me. A 14-month tour ensued ending in Seattle in 1988.
But the problems didn't stop there; in 1991 Clark was found dead in his London flat after binging on both drugs and alcohol. It was later revealed that the band had been trying for years to stop Clark's self-destructive habits without success.
Adreanalize (1992) was the next release, and an appearance at the Freddie Mercury tribute show in 1992 saw the introduction of Clark's replacement Vivian Campbell (ex-Dio/ex-Trinity/ex-Whitesnake) at a low-key Dublin gig. That album was followed up with Retro Active (1993) a "B"-sides and rarities release, as well as Vault (1995), a greatest hits collection. A new full studio album was released in 1996 in the form of Slang, a release that showcased their slick new radio friendly sound. Euphoria (1999) followed, with X (2002), the best of compilation, Rock Of Ages (2005) and Yeah! (2006).
On 28 April 2008, Def Leppard released their first album of new studio material in six years, Songs from the Sparkle Lounge. The album debuted at No. 5 on the Billboard 200 in the US. The first single was entitled Nine Lives and featured country singer Tim McGraw, who co-wrote the song with Joe Elliott, Phil Collen, and Rick Savage.
Def Leppard toured 41 US cities plus Toronto, Canada, during mid-2009 with Poison and Cheap Trick as well as the Download Festival with Whitesnake and ZZ Top.
In October 2008, Def Leppard played with country star Taylor Swift in a taped show in Nashville, Tennessee, called CMT Crossroads: Taylor Swift and Def Leppard. This was released as a DVD on 16 June 2009 exclusively at Wal-Mart.
In October 2009 the band announced that they would be cancelling the last leg of the 2009 North American tour, a total of 23 shows. The band cited, "unforeseen personal matters," as the reason for the cancellations. At the time, the band denied rumours about a breakup, saying, "We're not splitting. Not at all. We often joke, what else would we do? You just can't imagine doing anything else".
Their first live album was released in the summer of 2011 called Mirror Ball Live & More, a two-disc live album, with three new studio tracks. Their self-titled followed in 2015.
They became known as a band that has managed to stay alive in the NWOBHM field with a more Pop sound than Hard Rock by combining the raw power of metal with a pop emphasis on melody, catchy hooks and vocal harmonies that, particularly later on, contrasted sharply with harsher contemporary metal and punk bands.