Ellefson is of Norwegian ancestry.
Pre-Megadeth Ellefson played in a band called Killers, which featured himself on bass, Greg Handevidt on guitar, Brett Frederickson on drums and Jerry Giefer, during Frederickson's senior year of high school.
First tenure with Megadeth and initial departure (1983–2002) ,
Dave Mustaine,
Gar Samuelson and David Ellefson. Other than guitarist, vocalist, and primary lyricist
Dave Mustaine, Ellefson was the only constant member of Megadeth from early in the band's history in 1983 until the group's dissolution in 2002. Ellefson has maintained that he was a founding member of the band, though Mustaine has disputed the idea in multiple interviews. Mustaine referred to Ellefson as "Dave Junior", which was often shortened to "Junior" after vocalist Lor Kane used the nickname to differentiate between the two Daves. Ellefson appeared on every album and tour from 1985's record
Killing Is My Business... And Business Is Good! up until 2002's
Rude Awakening. Mustaine reformed Megadeth without Ellefson in 2004. In the early days of Megadeth, Ellefson played using his fingers, but as Megadeth progressed and the music became more complex, he tended to prefer playing with a pick, or
plectrum. Ellefson was credited with some Megadeth songs, including "Family Tree" from 1994's
Youthanasia (in the 2004 remastered collection of the CD, however, the track is credited to Mustaine, Ellefson,
Friedman,
Menza, but Mustaine credited the
Rust in Peace-era line-up with the entire
Youthanasia album as a tribute to the band's success at the time of the record's initial release).
Post-Megadeth career and return (2002–2010) Ellefson formed
F5 following Megadeth's 2002 disbandment. The band featured Ellefson on bass, Dale Steele on vocals, Steve Conley on lead guitar, John Davis on rhythm guitar, and former Megadeth bandmate
Jimmy DeGrasso on drums. Their first album,
A Drug for all Seasons, was released in 2005. F5 appeared in support for
Disturbed in February 2006 and toured the American Mid-West in the summer of 2006. Ellefson also appeared on the new Killing Machine record
Metalmorphosis in 2006 alongside DeGrasso; he has also been working with Temple of Brutality. Ellefson is currently a member of the melodic
power metal band
Avian, which features singer
Lance King. He commented in an interview with Alternative-Zine.com that "Megadeth was really just a starting point for me, creatively". Ellefson played five tracks for the
Soulfly album
Prophecy and also played on one track on
Dark Ages. He also worked with
underground emcee/Record producer
Necro for his album entitled
Death Rap. Ellefson is also a member of a cover band called
Hail!. Ellefson, DeGrasso (
Mike Portnoy for 2010),
Tim "Ripper" Owens and
Andreas Kisser formed the band in late 2008. The band was, as of April 2009, touring Europe. Ellefson participated in the Christmas Rock project
Northern Light Orchestra, he performed bass on many of the 17 tracks produced by rock drummer
Ken Mary and also at the live show Christmas in April
Orpheum Theatre,
Phoenix, Arizona. In February 2010, Ellefson received a text message from Megadeth drummer
Shawn Drover, saying "if ever there was a time for you and Dave [Mustaine] to talk, now is it". Ellefson was invited to rehearse with the band. After the phone call, the news was released that Ellefson would return to the Megadeth lineup. Ellefson was quoted saying "it felt like I never left" after their first rehearsal together.
Second tenure with Megadeth and departure (2010–2021) In 2013, Ellefson announced that his autobiography, entitled
My Life with Deth, would be issued by American publisher
Howard Books. The memoir was co-written with author
Joel McIver, and features a foreword by
Alice Cooper. In 2018, it was announced that Ellefson had begun work on
More Life with Deth, the follow-up to his 2013 memoir
My Life with Deth, to be co-written with Ellefson's business partner, and frequent collaborator,
Thom Hazaert. The book was released on July 16, 2019, by UK based Jawbone Press, and features contributions from
Alice Cooper,
K.K. Downing of
Judas Priest,
Dan Donegan of
Disturbed,
Brian Welch of
Korn,
Mark Slaughter,
Ron Keel, Jason McMaster of
Dangerous Toys,
Frank Bello of
Anthrax,
Chris Adler (
Lamb of God, ex-
Megadeth),
Mark Tremonti of
Creed and
Alter Bridge,
Kiko Loureiro and
Dirk Verbeuren of
Megadeth, actor
Kristian Nairn (
Game of Thrones), and more, plus a foreword by
My Life with Deth co-author, and
Bass Player Magazine editor
Joel McIver. In late 2018, he confirmed he was considered for the role of
Metallica bassist twice: in 1986, after
Cliff Burton was killed in a bus accident, and again in 2002 when bassist
Jason Newsted left the band a year earlier. He was not included in the documentary
Metallica: Some Kind of Monster showing musicians auditioning for the band, however, and after Newsted's departure the position was ultimately filled by
Robert Trujillo (former
Suicidal Tendencies,
Infectious Grooves and
Ozzy Osbourne). In 2019, Ellefson said since he rejoined Megadeth, he is a salaried member as opposed to being an "equal owner" with Mustaine in order to retain their friendship. In 2018 Ellefson was inducted into the
Iowa Rock 'n' Roll Hall of Fame. The following year in 2019 he was inducted into the
Metal Hall of Fame, he has since joined the Hall of Fames board of directors. On May 24, 2021, Dave Mustaine released a statement on behalf of the band that David Ellefson had once again parted ways with Megadeth, following allegations of sexual misconduct with an underage fan. Ellefson denied any wrongdoing, and the other party denied being underage and said explicit videos were released without her consent. On June 17, 2021, Dave Mustaine announced in his weekly
Gimme Radio show that he intended to hire a new bassist to rerecord Ellefson's bass tracks for Megadeth's 2022 album
The Sick, the Dying... and the Dead! Ellefson's parts were overdubbed by
Steve Di Giorgio of
Testament. Former Megadeth bassist
James LoMenzo, who Ellefson replaced in 2010, would rejoin Megadeth in 2022 as Ellefson's full-time replacement.
Post Megadeth projects (2021–present) Following his departure from Megadeth, Ellefson formed a new band named
The Lucid. With Ellefson on bass, the band also consists of drummer
Mike Heller (
Fear Factory,
Malignancy), guitarist
Drew Fortier, and vocalist
Vinnie Dombroski (
Sponge,
Spys4Darwin). Between September and October 2021, the band released three singles; "Maggot Wind", "Damned", and "
Hair". Their self-titled debut,
The Lucid, was released on October 15, 2021. In January 2023, the Lucid released their sophomore effort, a five-track EP titled
Saddle Up and Ride. The EP includes a guest performance from
Insane Clown Posse vocalist
Violent J on the title track as well as a cover of
Faith No More's "
Epic" retitled as "Sweet Toof". Between December 2022 and January 2023, four singles from the EP were released; "Saddle Up and Ride", "Mumps", "Risk Machine", and "Sweet Toof". In 2022, Ellefson formed the death metal band Dieth with Guilherme Miranda on guitar and vocals and Michał Łysejko on drums. The band released their first single,
In the Hall of the Hanging Serpents, on July 13, 2022. The band released three more singles and their first album
To Hell and Back in 2023. Song
Walk With Me Forever from the same album marks Ellefson's first time in his career singing lead vocals. In 2022, Ellefson formed the band Kings Of Thrash with former Megadeth guitarist
Jeff Young. The band plays songs from the first three studio albums of Megadeth live (and sometimes Mustaine-penned Metallica tunes, such as "
Jump In The Fire"). They had former Megadeth guitarist
Chris Poland as a guest on their
The MEGA Years tour in 2022. In February 2023, the group also played shows with an early guitarist for Megadeth, Greg Handevidt. In April 2024, Ellefson filled in for bassist
D.D. Verni on
Overkill's Latin American tour when Verni was unable to perform as he was recovering from shoulder surgery. On November 21, 2025, it was announced that Ellefson had joined
Metal Church as their new bassist, and he performed on the band's fourteenth studio album
Dead to Rights, which was released on April 10, 2026. ==Other ventures==