Billie was born in Los Angeles, California, on December 18, 2001.
She is the daughter of actress and screenwriter Maggie Baird and actor Patrick O'Connell, both of whom are also musicians.
In October 2015, Eilish recorded the song "Ocean Eyes", written and produced by Finneas originally for his band, after her dance teacher asked them to record a song for a dance routine. They released the song on SoundCloud, as they had already done with a couple of songs they wrote.
A music video for "Ocean Eyes" was released in March 2016.
By August 2016, Eilish had signed to the record label and artist management company The Darkroom, an imprint of Interscope Records.
On January 14, 2017, Eilish released an EP with four remixes of "Ocean Eyes".
Following the success of the "Ocean Eyes" remixes, Eilish released the single "Bellyache" on February 24, 2017
In February 2018, Eilish embarked on the Where's My Mind Tour, which concluded in April 2018.
For Record Store Day 2018, Eilish released a 7" vinyl featuring an acoustic version of her song "Party Favor" and an acoustic cover of Drake's "Hotline Bling".
In October 2018, Eilish released the single "When the Party's Over", and signed a modeling contract with Next Models.
In early January 2019, Eilish's EP Don't Smile at Me reached 1 billion streams on Spotify, making her the youngest artist to top 1 billion streams on a project.
Eilish released "Bury a Friend" as the third single from her upcoming debut album When We All Fall Asleep, Where Do We Go?
When We All Fall Asleep, Where Do We Go? was released on March 29, 2019.
"Bad Guy", was released in conjunction with the album.
On November 20, 2019, Eilish was nominated for six Grammy Awards including Record of the Year and Song of the Year for "Bad Guy" as well as Album of the Year and Best New Artist. At the age of 17, she became the youngest artist to be nominated in all four General Field categories.
On January 14, 2020, Eilish was announced as performer of the title track for the twenty-fifth installment in the James Bond film franchise, No Time to Die, written and produced with her brother, Finneas O'Connell.