Megadeth is an American heavy metal band from Los Angeles, California, formed in 1983. Founded by guitarist/vocalist Dave Mustaine and bassist David Ellefson following Mustaine's departure from Metallica, the band has since released 12 studio albums, three live albums, two EPs, 26 singles, 32 music videos, four compilations and one box set. As a pioneer of the American thrash metal movement, Megadeth rose to international fame in the 1980s and was ranked as one of the "Big Four of Thrash," along with Metallica, Slayer, and Anthrax, who were responsible for creating, developing and popularizing the thrash metal sub-genre.

Megadeth has experienced numerous line-up changes, due partly to the band's notorious substance abuse problems. From 1983 to 2002 - and as of February 8, 2010 - Mustaine and Ellefson are the only original members of the band, with Mustaine being the only constant member. After finding sobriety and securing a stable line-up, Megadeth went on to release a string of platinum and gold albums, including the platinum-selling landmark Rust in Peace in 1990 and the Grammy nominated, multi-platinum Countdown to Extinction in 1992.

Megadeth disbanded in 2002 after Mustaine suffered a severe nerve injury to his left arm. However, following extensive physical therapy, Mustaine reformed the band in 2004 and released The System Has Failed, followed by United Abominations in 2007; the albums debuted on the Billboard Top 200 chart at #18 and #8, respectively. Megadeth, along with their new lead guitarist Chris Broderick, released their twelfth studio album, titled Endgame, on September 15, 2009, which debuted at #9 on the Billboard 200, marking Megadeth's fifth top 10 album.

In the band's 25 active years, there have been over 20 individuals that have all officially been a part of the group at different times, with Dave Mustaine and David Ellefson being the only original members. Megadeth is known for its distinctive, technical instrumental style, often featuring dense, intricate passages and trade off guitar solos, as well as for Mustaine's recurring lyrical themes including politics, war, addiction, personal relationships and religious themes. Megadeth has sold over 25 million albums worldwide, with five consecutive albums being certified platinum or multi-platinum in the USA. The band has also been nominated nine consecutive times for Best Metal Performance.