| Period | Members | Studio releases |
| April–June 1983(as Fallen Angels) | Dave Mustaine – guitar Matt Kisselstein – bass Lor Kane – vocals Robbie McKinney – guitar | none – rehearsals only |
| ca. June 1983(as Megadeth) | Dave Mustaine – guitar Matt Kisselstein – bass Lor Kane – vocals Robbie McKinney – guitar |
| ca. June 1983 | Dave Mustaine – guitar Lor Kane – vocals Greg Handevidt – guitars |
| ca. June 1983 | Dave Mustaine – guitar Lor Kane – vocals David Ellefson - bass Greg Handevidt – guitars |
| June–July 1983 | Dave Mustaine – guitar Lor Kane – vocals David Ellefson – bass Dijon Carruthers – drums |
| Summer 1983 | Dave Mustaine – lead guitar Lor Kane – vocals David Ellefson – bass Greg Handevidt – guitar Dijon Carruthers – drums |
| Summer 1983 | Dave Mustaine – lead guitar Lor Kane – vocals David Ellefson – bass Greg Handevidt – guitar Richard Girod – drums | Unreleased demo |
| July–August 1983 | Dave Mustaine – guitar David Ellefson – bass Greg Handevidt – guitar Richard Girod – drums | none – rehearsals only |
| August–September 1983 | Dave Mustaine – guitar David Ellefson – bass Greg Handevidt – guitar Dijon Carruthers – drums |
| September–November 1983 | Dave Mustaine – guitar David Ellefson – bass Dijon Carruthers – drums John Cyriis – vocals |
| November–December 1983 | Dave Mustaine – guitar David Ellefson – bass Brett Frederickson – drums |
| ca. December 1983 | Dave Mustaine – guitar David Ellefson – bass, backing vocals Lee Rauch – drums Billy Bonds – vocals |
| December 1983 − April 1984 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Lee Rauch – drums Kerry King – guitar (touring) | none – live shows and rehearsals |
| April–July 1984 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Lee Rauch – drums | none – rehearsals and 1984 demo |
| July–October 1984 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals | none – rehearsals only |
| October–December 1984 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Gar Samuelson – drums | none – live shows only |
| December 1984 – July 1985 | Dave Mustaine – guitar, piano, vocals David Ellefson – bass, backing vocals Gar Samuelson – drums Chris Poland – guitar | Killing Is My Business... and Business Is Good! (1985) |
| July–October 1985 | Dave Mustaine – guitar, piano, vocals David Ellefson – bass, backing vocals Gar Samuelson – drums Mike Albert – guitar | none – live shows only |
| October 1985 – June 1987 | Dave Mustaine – guitar, piano, vocals David Ellefson – bass, backing vocals Gar Samuelson – drums Chris Poland – guitar | Peace Sells... but Who's Buying? (1986) "These Boots Are Made for Walkin (1987)(Dudes soundtrack) |
| June–October 1987 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Chuck Behler – drums Jay Reynolds – guitar | none – rehearsals only |
| October 1987 – January 1989 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Chuck Behler – drums Jeff Young – guitar | So Far, So Good... So What! (1988) |
| January 1989 – July 1989 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Chuck Behler – drums | Rust in Peace demos |
| July 1989 – November 1989 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Nick Menza – drums, backing vocals | "No More Mr. Nice Guy" (1989)(Shocker soundtrack) |
| November 1989 – February 1990 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Nick Menza – drums, backing vocals Chris Poland – guitar | Rust in Peace demos |
| February 1990 – July 1998 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Nick Menza – drums, backing vocals Marty Friedman – guitar, backing vocals | Rust in Peace (1990) "Go To Hell" (1991) (Bill & Ted's Bogus Journey soundtrack) Countdown to Extinction (1992) "Breakpoint" (1993) (Super Mario Bros. soundtrack) "Angry Again" (1993) (Last Action Hero soundtrack) "99 Ways to Die" (1993) (The Beavis and Butt-Head Experience) "Paranoid" (1994) (Nativity in Black: A Tribute to Black Sabbath) Youthanasia (1994) "Diadems" (1995) (Demon Knight soundtrack) One new track on Hidden Treasures (1995) Cryptic Writings (1997) |
| July 1998 – January 2000 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Marty Friedman – guitar, backing vocals Jimmy DeGrasso – drums | "Never Say Die" (1999) (Nativity in Black II: A Tribute to Black Sabbath) Risk (1999) |
| January 2000 – April 2002 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Jimmy DeGrasso – drums Al Pitrelli – guitar, backing vocals | Three new tracks on Capitol Punishment: The Megadeth Years (2000) The World Needs a Hero (2001) |
| Inactive from April 2002 – October 2003 |
| October 2003 – May 2004 | Dave Mustaine – guitar, vocals (session) Chris Poland – guitar (session) Jimmie Lee Sloas – bass (session) Vinnie Colaiuta – drums (session) | none – sessions only |
| May–July 2004 | Dave Mustaine – guitar, vocals (session) Chris Poland – guitar (session) Jimmie Lee Sloas – bass (session) Vinnie Colaiuta – drums (session) Tim Akers – keyboards (session) Charlie Judge – keyboards (session) Chris Rodriguez – backing vocals (session) | The System Has Failed (2004) |
| July–September 2004 | Dave Mustaine – guitar, vocals Nick Menza – drums, backing vocals | none – rehearsals only |
| September–October 2004 | Dave Mustaine – guitar, vocals Nick Menza – drums, backing vocals James MacDonough – bass, backing vocals Glen Drover – guitar, backing vocals |
| October 2004 – February 2006 | Dave Mustaine – guitar, vocals James MacDonough – bass, backing vocals Glen Drover – guitar, backing vocals Shawn Drover – drums | none – live shows only |
| February–April 2006 | Dave Mustaine – guitar, vocals Glen Drover – guitar, backing vocals Shawn Drover – drums James LoMenzo – bass, backing vocals |
| April 2006 – January 2007 | Dave Mustaine – guitar, vocals Chris Rodriguez – backing vocals (session) Glen Drover – guitar, backing vocals Shawn Drover – drums, backing vocals James LoMenzo – bass, backing vocals Axel Mackenrott – keyboards (session) | United Abominations (2007) |
| January–November 2007 | Dave Mustaine – guitar, vocals Glen Drover – guitar, backing vocals Shawn Drover – drums James LoMenzo – bass, backing vocals | none – live shows only |
| November 2007 – February 2010 | Dave Mustaine – guitar, piano, vocals Shawn Drover – drums, backing vocals James LoMenzo – bass, backing vocals Chris Broderick – guitar, backing vocals | Endgame (2009) |
| February 2010 – November 2011 | Dave Mustaine – guitar, vocals Chris Rodriguez – backing vocals (session) Shawn Drover – drums, backing vocals Chris Broderick – guitar, backing vocals David Ellefson – bass, backing vocals | Thirteen (2011) |
| November 2011 – November 2014 | Dave Mustaine – guitar, vocals Shawn Drover – drums, backing vocals Chris Broderick – guitar, backing vocals David Ellefson – bass, backing vocals | Super Collider (2013) |
| December 2014 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Nick Menza – drums | none – rehearsals only |
| 2014 | Dave Mustaine – guitar David Ellefson – bass, backing vocals Nick Menza – drums | Dystopia demos |
| April–July 2015 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Kiko Loureiro – guitar, backing vocals Chris Adler – drums Charlie Judge – keyboards (session) Blair Masters – keyboards (session) Chris Rodriguez – backing vocals (session) | Dystopia (2016) |
| July 2015 – October 2015 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Kiko Loureiro – guitar, backing vocals Chris Adler – drums Tony Laureano – drums (touring) |
| May–July 2016 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Kiko Loureiro – guitar, piano, backing vocals Chris Adler – drums Dirk Verbeuren – drums (touring) | none – live shows only |
| July 2016 – May 2021 | Dave Mustaine – guitar, vocals David Ellefson – bass, backing vocals Kiko Loureiro – guitar, piano, backing vocals Dirk Verbeuren – drums |
| May–June 2021 | Dave Mustaine – guitar, vocals, bass Kiko Loureiro – guitar, piano, backing vocals, flute Dirk Verbeuren – drums | The Sick, the Dying... and the Dead! (2022) |
| June–August 2021 | Dave Mustaine – guitar, vocals Kiko Loureiro – guitar, piano, backing vocals, flute Dirk Verbeuren – drums Steve Di Giorgio – bass (session) |
| August–December 2021 | Dave Mustaine – guitar, vocals Kiko Loureiro – guitar, piano, backing vocals, flute Dirk Verbeuren – drums Steve Di Giorgio – bass (session) James LoMenzo – bass, backing vocals (touring) |
| December 2021 – November 2023 | Dave Mustaine – guitar, vocals Kiko Loureiro – guitar, piano, backing vocals Dirk Verbeuren – drums James LoMenzo – bass, backing vocals (touring till May 2022) Teemu Mäntysaari – guitar, backing vocals (touring September 2023) | "Delivering the Goods" (2023) (single) |