Billie Eilish Pirate Baird O'Connell was born in Los Angeles, California, on December 18, 2001. She is the daughter of actress and teacher Maggie Baird and actor Patrick O'Connell, both of whom are also musicians and work on Eilish's tours. Eilish is of Irish and Scottish descent. Her middle name, Eilish, was chosen by her parents while watching a documentary about Irish conjoined twins Katie and Eilish Holton and was originally meant to be her first name, while Pirate was to have been her middle name. After her grandfather William Baird died while her mother was pregnant, her parents decided to name her Billie, after him. She grew up in Los Angeles's Highland Park neighborhood. Naturally blonde, Eilish has been dyeing her hair since she was nine years old, starting with a Manic Panic shade of blue. She generally prefers it to be black, which feels most "like [her]".

Eilish and her older brother Finneas were homeschooled by Baird, a decision their parents made to spend time with them and give them the freedom to pursue their interests. Baird taught Eilish and Finneas the basics of songwriting. Eilish said her brother and mother inspired her to get into music. Their parents encouraged the siblings to express themselves and explore whatever they wanted, including art, dancing, and acting.

Eilish started playing the ukulele at age six. She performed at talent shows and joined the Los Angeles Children's Chorus at age eight. She wrote her first "real" song at age 11 for her mother's songwriting class. The song is about the zombie apocalypse, inspired by the television series The Walking Dead, from which she took script lines and episode titles. Eilish took some acting auditions, which she disliked, but she enjoyed recording background dialogue for crowd scenes and worked on the films Diary of a Wimpy Kid, Ramona and Beezus, and the X-Men series. Eilish also took dance classes until 2016, when a growth plate injury ended her dance career and she focused on recording music.

In 2015, 13-year-old Eilish began working on songs with her brother Finneas, who had been writing and producing for several years and had his own band. The first songs they recorded together were called "She's Broken" and "Fingers Crossed", the former written by Finneas and the latter by Eilish. "We recorded them and put them out on SoundCloud, just for fun", she recalled.

On November 18, 2015, Eilish released the song "Ocean Eyes". The track was written, mixed, and produced by Finneas, who had originally created it for his band the Slightlys before deciding it would be a better fit for Eilish's vocals. He gave it to Eilish when Fred Diaz, her dance teacher at the Revolution Dance Center, asked them to write a song for choreography. The siblings uploaded the song to SoundCloud, where Diaz could access and download it. The song received several hundred thousand listens in two weeks, and Finneas's manager, Danny Rukasin, reached out to him to discuss Eilish's potential. Rukasin felt she could achieve significant success with Finneas's help.

In January 2016, Finneas and his manager arranged a deal in which Apple Music signed Eilish to A&R company Platoon, specializing in packaging emerging artists before they get a major-label contract. Eilish then hired a publicist, who connected her to the luxury fashion brand Chanel, and a stylist, both of whom helped shape her image. On March 24, 2016, a music video for "Ocean Eyes" directed by Megan Thompson premiered on Eilish's official YouTube channel. "Ocean Eyes" and Eilish received praise and promotion from various media outlets and marketers, including radio stations and music supervisors such as Beats 1, KCRW, BBC Radio 1, Zane Lowe, Jason Kramer, Annie Mac, and Chris Douridas. On June 23, 2016, Eilish and Finneas released "Six Feet Under" on SoundCloud as her second single. A homemade music video for the song was released on June 30, 2016. It was directed by Eilish and edited by her mother, Maggie Baird.

In August 2016, Justin Lubliner, who had noticed Eilish's talent in 2015 when he first heard "Ocean Eyes", signed her to Darkroom and Interscope Records. He developed her rollout as an artist, taking inspiration from the model of hip hop artists such as Travis Scott and Chance the Rapper, not relying on one big single and focusing on creating a "persona and distinct aesthetic". Darkroom and Interscope Records re-released "Six Feet Under" and "Ocean Eyes" as singles for digital download and streaming on November 17 and 18, 2016, respectively. On November 22, 2016, a dance performance music video for "Ocean Eyes" was uploaded to Eilish's YouTube channel.

On January 14, 2017, Eilish released an EP with four remixes by Astronomyy, Blackbear, Goldhouse, and Cautious Clay for "Ocean Eyes", and another EP for "Six Feet Under" featuring remixes by Blu J, Gazzo, Jerry Folk, and Aire Atlantica. After the success of the "Ocean Eyes" remixes, Eilish released "Bellyache" on February 24, 2017. A video for the song was released on March 22, 2017, directed by Miles and AJ. Eilish released "Bored" on March 30, 2017, as part of the soundtrack to the Netflix series 13 Reasons Why. A video for "Bored" was released on June 26, 2017. In March of the same year, Apple Music showcased Eilish at the South by Southwest music festival. On June 30, 2017, Eilish released "Watch". Eilish released another single, "Copycat", on July 14, 2017, and announced the release of her debut EP, Don't Smile at Me. Eilish later released "Idontwannabeyouanymore" and "My Boy". On August 11, 2017, Eilish released Don't Smile at Me. The EP was a sleeper hit, reaching number 14 on the US Billboard 200. Eilish embarked on the Don't Smile at Me Tour throughout October 2017 in support of her EP. Eilish released "Bitches Broken Hearts" through SoundCloud on November 10, 2017.

Eilish's team worked with Spotify, which promoted her on its most popular playlist, "Today's Top Hits". The Baffler described Eilish's sound as fitting into the "streambait" genre consisting of largely "mid-tempo, melancholy pop" influenced by Lana Del Rey, whose "singing style, bleakness, and... hip-hop influenced production" shaped the aesthetic. Eilish's commercial success expanded with her Spotify promotion. In September 2017, Apple Music named Eilish their Up Next artist, which followed with a short documentary, a live session EP, and an interview with Zane Lowe on Apple Music's radio station Beats 1. That month, the live EP, Up Next Session: Billie Eilish, was released. On December 15, 2017, Eilish released her collaboration with American rapper Vince Staples, "&Burn", a remix of her single "Watch". It was included on the expanded edition of Don't Smile at Me.

In February 2018, Eilish embarked on her second headlining concert tour, the Where's My Mind Tour, which concluded in April 2018. "Bitches Broken Hearts" was re-released worldwide on March 30, 2018. For Record Store Day 2018, Eilish released "Party Favor" on a pink 7-inch vinyl, along with a cover of "Hotline Bling", by Drake, as the B-side. Eilish collaborated with American singer Khalid on the single "Lovely", which was released on April 19, 2018, and added to the soundtrack for the second season of 13 Reasons Why. She released "You Should See Me in a Crown" in July 2018. The same month, Eilish performed at the Mo Pop Festival.

On the day of release for her single "When the Party's Over", Eilish was featured in Vanity Fair's "73 Questions" rapid-fire questionnaire video series by Joe Sabia, who revisited an interview from October 2017. The resulting video was a side-by-side time capsule of both interviews showing her growth in popularity over one year. She signed a talent contract with Next Management for fashion and beauty endorsements in October 2018. She was placed on the 2018 Forbes 30 Under 30 list in November of that year, and released the single "Come Out and Play" in November 2018, which was written for a holiday-themed Apple Inc. commercial. In early January 2019, Don't Smile at Me reached 1 billion streams on Spotify, making her the youngest artist to top 1 billion streams on a project. That month, Eilish released "Bury a Friend" as the third single from her debut album When We All Fall Asleep, Where Do We Go?, along with "When I Was Older", a single inspired by the 2018 film Roma, which appeared on the compilation album Music Inspired by the Film Roma. In February, Eilish partnered with YouTube on a documentary miniseries, "A Snippet Into Billie's Mind". "Wish You Were Gay", her fourth single from the album, was released on March 4, 2019.

When We All Fall Asleep, Where Do We Go? was released on March 29, 2019. Spotify launched a "multi-level campaign behind the album", creating a multimedia playlist and "new product features" that Spotify said "allow for vertical video content, custom assets, and editorial storylines, all with the goal of creating more meaningful and engaging context for [Eilish's] fans." In Los Angeles, Spotify set up a "pop-up enhanced album experience", which included different artwork and a "multi-sensory" experience of each track for fans. The album debuted atop the Billboard 200 as well as on the UK Albums Chart, making Eilish the first artist born in the 2000s to have a number-one album in the US and the youngest female ever to have a number-one album in the United Kingdom. Upon the album's debut, Eilish broke the record for most simultaneously charting Hot 100 songs by a female artist, with 14, after every song from the album, excluding "Goodbye", charted on the Hot 100. The fifth single from the album, "Bad Guy", was released in conjunction with the album. A remix of the song featuring Justin Bieber was released in July 2019. In August, "Bad Guy" peaked at number-one in the US, ending Lil Nas X's record-breaking 19 weeks at number-one with "Old Town Road". She is the first artist born in the 2000s and the youngest artist since Lorde (with "Royals") to have a number-one single.

Eilish began her When We All Fall Asleep Tour at Coachella Festival in April 2019, with the tour concluding on November 17, 2019, in Mexico City. In August 2019, she partnered with Apple Music for Music Lab: Remix Billie Eilish, part of Apple Stores' Music Lab sessions during which fans deconstruct her song "You Should See Me In A Crown" and learn how to create their own remix on Apple devices and GarageBand. On September 27, 2019, Eilish announced her Where Do We Go? World Tour. The tour began in Miami on March 9, 2020, and ran for two more shows on March 10 in Orlando and March 12 in Raleigh before Eilish ended the tour prematurely due to the COVID-19 pandemic. The tour was set to conclude in Jakarta on September 7.

On November 7, 2019, Jack White's Third Man Records announced that the label would release an acoustic live album of Eilish's performance from the record label's Blue Room, exclusively sold on vinyl at Third Man retail locations in Nashville, Tennessee, and Detroit, Michigan. On November 13, 2019, she released her next single, "Everything I Wanted". 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 age 17, she became the youngest artist to be nominated in all four General Field categories. In the same month, Eilish was crowned 2019's Billboard Woman of the Year.

On January 14, 2020, Eilish was announced as performer of the title track for the 25th installment in the James Bond film franchise, No Time to Die, written and produced with her brother. With this announcement, Eilish became the youngest artist to write and perform a James Bond theme song. It became the second Bond theme song to top the British official charts and the first Bond theme performed by a female artist to do so. It was also Eilish's first number-one single in the UK. At the 62nd Annual Grammy Awards, she became the youngest person to win the four main Grammy categories – Best New Artist, Record of the Year, Song of the Year, and Album of the Year – in the same year. During the COVID-19 pandemic, Eilish and her brother performed for both iHeart Media's Living Room Concert for America, and Global Citizen's Together at Home concert series, singing a cover of Bobby Hebb's "Sunny" for the latter. Both virtual concerts were an effort to raise awareness and funds towards fighting the disease. On April 10, 2020, "Ilomilo" was sent to Italian contemporary hit radio stations by Universal Music Group, as When We All Fall Asleep, Where Do We Go?'s seventh and final single. On July 30, 2020, Eilish released "My Future", her first original release since "No Time to Die", along with an animated video. In 2020, she became the youngest person to feature on the Forbes Celebrity 100 list, with earnings of $53 million. In September 2020, Eilish released a collection of branded ukuleles with guitar manufacturer Fender.

On October 7, 2020, Eilish announced a virtual concert titled Where Do We Go? The Livestream. Staged in Los Angeles on October 24, the performance utilised extended reality (XR) technology and featured drummer Andrew Marshall and Eilish's brother, Finneas. Ticket proceeds were used to support touring crew members affected by COVID-19 cancellations via Crew Nation. In a Vanity Fair interview, Eilish said she was working on "sixteen new songs and lov[ing] them all", revealing an upcoming musical project. Eilish won three Billboard Music Awards on October 24—Top Female Artist, Top Billboard 200 Album (When We All Fall Asleep, Where Do We Go?), and Top New Artist—out of the 12 that she was nominated for. Also that month, she announced a new single, "Therefore I Am", which was released along with its video on November 12, 2020. Eilish performed "Therefore I Am" and "My Future" at the Jingle Ball in December 2020.

"Lo Vas a Olvidar", a single featuring Rosalía as part of HBO's Euphoria soundtrack, was released in January 2021, for the special "Fuck Anyone Who's Not a Sea Blob". On February 26, 2021, the R. J. Cutler-directed documentary film Billie Eilish: The World's a Little Blurry was released on Apple TV+ and in select movie theaters. The film was praised by critics and fans for its in-depth look at Eilish's personal life during her ascent to fame. At the 63rd Annual Grammy Awards, Eilish took home two awards: Best Song Written for Visual Media for her Bond theme and Record of the Year for "Everything I Wanted". In her acceptance speech for Record of the Year, Eilish said that Megan Thee Stallion "deserved to win", but still thanked her fans and her brother for her award. In 2021, she published her personally selected comprehensive book of photographs that shared "an intimate window into her life" on and off stage, By – Billie Eilish.

On April 27, 2021, Eilish announced on her Instagram account that her second album, Happier Than Ever, would be released on July 30, and the tracklist was made available on Apple Music. The album was released in various formats, including collectible vinyl and cassette colors. The album's release was preceded by five singles: "My Future", "Therefore I Am", "Your Power", "Lost Cause", and "NDA", and was accompanied by the title track. On December 2, 2021, Eilish announced an eco-friendly limited-edition vinyl version of Happier Than Ever made from recycled vinyl scraps. The collector's item was available only at a number of Gucci stores around the world and included Gucci-branded nail stickers designed by the brand's creative director, Alessandro Michele. To further promote the album, Eilish worked with Disney+ on the concert film Happier Than Ever: A Love Letter to Los Angeles, released in September 2021, and embarked on the Happier Than Ever, The World Tour in February 2022, concluding it in April 2023.

In June 2021, Eilish was criticized online for videos in which she mouthed the anti-Asian slur "chink" while lip-syncing the song "Fish" by Tyler, the Creator, while Matthew Tyler Vorce, her reported boyfriend at the time, received criticism for alleged social media posts in which he used offensive language and slurs against gay and Black people. Eilish was also accused of queerbaiting after using the caption "I love girls" to promote the music video for "Lost Cause". On June 22, she posted an apology to Instagram stories for her usage of "chink", saying that she was "appalled and embarrassed" by the video and that she was "13 or 14" at the time and did not know the slur was a derogatory term. She also addressed a separate video of what was viewed as her mocking an Asian accent, writing that she was actually "speaking in a silly gibberish made up voice". Reflecting on the events in a July 2021 interview, Eilish said: "I said so many things then that I totally don't agree with now, or think the opposite thing. The weirdest thing is how nothing ever goes away once it's on the internet ... When you're a fucking teenager, you don't really know yourself ... I didn't actually know how I really felt. So I just came up with this facade that I stuck to."

Eilish started formulating ideas for her third studio album's songs with Finneas in December 2021. In a July 2022 interview with Zane Lowe for Apple Music, she said she hoped to start writing the album in 2023. In 2022, Eilish won the Academy Award for Best Original Song for the song "No Time to Die" from the film No Time to Die, becoming the first person born in the 21st century to win an Academy Award. That same year, she became the youngest headliner to date for two festivals, specifically Glastonbury and Coachella. The Pixar film Turning Red was released that year, for which she and Finneas wrote three songs, "Nobody Like U", "U Know What's Up" and "1 True Love", performed by Turning Red's fictional boy band 4*Town.

In June 2022, during her world tour's Manchester show, Eilish debuted the then-unreleased ballad "TV". The song references the overturning of Roe v. Wade, a case that made abortion a constitutional right in the US. The next month, on July 21, she surprise-released the two-track EP Guitar Songs, which includes "TV" alongside "The 30th". Eilish explained her decision to surprise-release the EP during the interview with Lowe. She told him that while work on her third studio album was coming soon, she refused to wait until that time to put "TV" and "The 30th" on a track list. She wanted to spread their messages to her fans as soon as possible, noting the immediacy of its lyrics: "These songs are really current for me, and they're songs that I want to have said right now." Another reason was Eilish had grown tired of doing heavy, traditional promotion for upcoming music. She wanted to release songs like she had early in her career, previewing them for fans in live concerts before releasing them without much marketing.

Eilish worked with Apple Music to exclusively host a film of one of the Happier Than Ever tour concerts, specifically one of her shows at The O2 Arena in London. She billed the film as a way for fans who missed out on tickets to experience the tour, wanting more people to recognize her showmanship live. Three concerts, titled Happier Than Ever, The Hometown Encore, were held at the Kia Forum in Inglewood, California, from December 13 to 16, 2022, as part of the tour.

In 2023, Eilish made her acting debut in the Amazon Prime Video satirical thriller series Swarm. She starred as Eva, the leader of a cult inspired by NXIVM, and received positive reviews for her performance. Eilish wrote the song "What Was I Made For?" for the soundtrack of the 2023 film Barbie. According to statements posted on her social media, she was inspired to write the song after seeing unfinished scenes of the movie during its production. In 2024, the song won the Academy Award for Best Original Song and two Grammy Awards for Song of the Year and Best Song Written for Visual Media. It became the tenth song in history to win both an Academy Award for Best Original Song and a Grammy Award for Song of the Year, and Eilish became the youngest person ever to win two Academy Awards in any category.

On April 8, 2024, Eilish announced her third studio album, Hit Me Hard and Soft, which was released on May 17, 2024. She announced a tour to support the album, Hit Me Hard and Soft: The Tour, on April 29, 2024, with concerts in North America, Oceania and Europe between September 2024 and July 2025. Also in April, Eilish was announced to be the next "featured artist" inside the Fortnite spin-off game Fortnite Festival, along with an unlockable outfit in the game. While on a visit to London due to the success of the recently released album in the UK, Eilish appeared alongside London-based content creator Amelia Dimoldenberg on her web series Chicken Shop Date, which was dubbed as the "flirtiest episode yet", and also appeared as a guest host for children's channel CBeebies' bedtime story. In August, Eilish featured on a remix of Charli XCX's "Guess", a song from the deluxe version of the latter's album Brat, accompanied by a video containing scenes of Eilish in a bulldozer and the pair surrounded by piles of women's underwear, which were donated to the charity I Support the Girls. On August 11, 2024, Eilish performed "Birds of a Feather" on Belmont Shore, Long Beach, during the 2024 Summer Olympics closing ceremony as part of the handover to Los Angeles, which would host the Games in 2028.

In March 2026, it was reported that Eilish was in "advanced talks" to make her film acting debut as lead character Esther Greenwood in a Sarah Polley-directed adaptation of Sylvia Plath's The Bell Jar. Eilish's Hit Me Hard and Soft: The Tour (Live in 3D) concert film, which she co-directed and produced with James Cameron, was theatrically released on May 8, 2026.

Eilish grew up listening to the Beatles, Justin Bieber, Green Day, the 1975, Arctic Monkeys, Nine Inch Nails, Linkin Park and Lana Del Rey. She has named the Beatles as her greatest musical inspiration, crediting the band for inspiring "95% of [her] love for music". She has said that stumbling upon Aurora's "Runaway" on YouTube inspired her to pursue a music career. Hip hop is her favorite genre of music.

She has recounted that Matty Healy was an early inspiration for her: "His show is the second show I ever went to in my life. He changed so much about who I am, how I write music." She has also cited Tyler, the Creator, Childish Gambino, and Avril Lavigne as major musical and style influences. Other influences include Adele, Earl Sweatshirt, James Blake, Amy Winehouse, the Spice Girls, Lorde, Marina, Britney Spears, Nicki Minaj, XXXTentacion, and Twenty One Pilots. She has also shown appreciation for Paramore after inviting Hayley Williams to join her set during Williams's first Coachella set to perform an acoustic version of "Misery Business" and sing "Happier Than Ever". Eilish also named Rihanna as an inspiration for her style choices after she called fashion her "defense mechanism" during an acceptance speech. She has also credited Damon Albarn for changing the way she views art and music creation.

Eilish has been compared in the media to Lavigne, Lorde and Del Rey, the last of whom she says she does not want to be compared to, saying, "That woman has made her brand so perfect for her whole career and she shouldn't have to hear that." Eilish said that Ariana Grande's 2019 album Thank U, Next inspired her to continue making music.

Eilish lived with her parents in the Highland Park neighborhood of Los Angeles until 2019, when she moved out. She said she received a diagnosis of Tourette syndrome when she was 11 years old. She also has synesthesia and experienced depression. Eilish has also shared that she experienced sexual abuse as a child. She was raised vegetarian before becoming vegan.

Eilish prefers to keep her sexuality and personal relationships private, but is attracted to both men and women. From 2018 to 2019, she dated rapper Brandon Adams, who goes by the stage name 7:AMP. Eilish then dated actor Matthew Tyler Vorce from 2021 until 2022. She dated singer Jesse Rutherford from October 2022 to May 2023. Since 2025, Eilish has been in a relationship with Nat Wolff.

On a 2020 episode of the me and dad radio podcast, Eilish said: "When I was a little kid, I was super religious for no damn reason. My family never was religious. I didn't know anyone that was religious. And for some reason, as a little girl, I just was incredibly religious ... And then at one point, I don't know what happened. It just completely went away...[and I became] almost anti-religious for no reason." She said the experience made her more "open-minded" to other religions. Of her own religion, Eilish said: "I don't not believe and I don't do believe. I'm in a very neutral position. I'm open to every belief pretty much...[I love] the idea that there's a God. So why not? How would I know? I'm not going to say I know. I don't. Nobody knows."

Billie Eilish Pirate Baird O'Connell was born in Los Angeles, California, on December 18, 2001. She is the daughter of actress and teacher Maggie Baird and actor Patrick O'Connell, both of whom are also musicians and work on Eilish's tours. Eilish is of Irish and Scottish descent. Her middle name, Eilish, was chosen by her parents while watching a documentary about Irish conjoined twins Katie and Eilish Holton and was originally meant to be her first name, while Pirate was to have been her middle name. After her grandfather William Baird died while her mother was pregnant, her parents decided to name her Billie, after him. She grew up in Los Angeles's Highland Park neighborhood. Naturally blonde, Eilish has been dyeing her hair since she was nine years old, starting with a Manic Panic shade of blue. She generally prefers it to be black, which feels most "like [her]".

Eilish and her older brother Finneas were homeschooled by Baird, a decision their parents made to spend time with them and give them the freedom to pursue their interests. Baird taught Eilish and Finneas the basics of songwriting. Eilish said her brother and mother inspired her to get into music. Their parents encouraged the siblings to express themselves and explore whatever they wanted, including art, dancing, and acting.

Eilish started playing the ukulele at age six. She performed at talent shows and joined the Los Angeles Children's Chorus at age eight. She wrote her first "real" song at age 11 for her mother's songwriting class. The song is about the zombie apocalypse, inspired by the television series The Walking Dead, from which she took script lines and episode titles. Eilish took some acting auditions, which she disliked, but she enjoyed recording background dialogue for crowd scenes and worked on the films Diary of a Wimpy Kid, Ramona and Beezus, and the X-Men series. Eilish also took dance classes until 2016, when a growth plate injury ended her dance career and she focused on recording music.

In 2015, 13-year-old Eilish began working on songs with her brother Finneas, who had been writing and producing for several years and had his own band. The first songs they recorded together were called "She's Broken" and "Fingers Crossed", the former written by Finneas and the latter by Eilish. "We recorded them and put them out on SoundCloud, just for fun", she recalled.

On November 18, 2015, Eilish released the song "Ocean Eyes". The track was written, mixed, and produced by Finneas, who had originally created it for his band the Slightlys before deciding it would be a better fit for Eilish's vocals. He gave it to Eilish when Fred Diaz, her dance teacher at the Revolution Dance Center, asked them to write a song for choreography. The siblings uploaded the song to SoundCloud, where Diaz could access and download it. The song received several hundred thousand listens in two weeks, and Finneas's manager, Danny Rukasin, reached out to him to discuss Eilish's potential. Rukasin felt she could achieve significant success with Finneas's help.

In January 2016, Finneas and his manager arranged a deal in which Apple Music signed Eilish to A&R company Platoon, specializing in packaging emerging artists before they get a major-label contract. Eilish then hired a publicist, who connected her to the luxury fashion brand Chanel, and a stylist, both of whom helped shape her image. On March 24, 2016, a music video for "Ocean Eyes" directed by Megan Thompson premiered on Eilish's official YouTube channel. "Ocean Eyes" and Eilish received praise and promotion from various media outlets and marketers, including radio stations and music supervisors such as Beats 1, KCRW, BBC Radio 1, Zane Lowe, Jason Kramer, Annie Mac, and Chris Douridas. On June 23, 2016, Eilish and Finneas released "Six Feet Under" on SoundCloud as her second single. A homemade music video for the song was released on June 30, 2016. It was directed by Eilish and edited by her mother, Maggie Baird.

In August 2016, Justin Lubliner, who had noticed Eilish's talent in 2015 when he first heard "Ocean Eyes", signed her to Darkroom and Interscope Records. He developed her rollout as an artist, taking inspiration from the model of hip hop artists such as Travis Scott and Chance the Rapper, not relying on one big single and focusing on creating a "persona and distinct aesthetic". Darkroom and Interscope Records re-released "Six Feet Under" and "Ocean Eyes" as singles for digital download and streaming on November 17 and 18, 2016, respectively. On November 22, 2016, a dance performance music video for "Ocean Eyes" was uploaded to Eilish's YouTube channel.

On January 14, 2017, Eilish released an EP with four remixes by Astronomyy, Blackbear, Goldhouse, and Cautious Clay for "Ocean Eyes", and another EP for "Six Feet Under" featuring remixes by Blu J, Gazzo, Jerry Folk, and Aire Atlantica. After the success of the "Ocean Eyes" remixes, Eilish released "Bellyache" on February 24, 2017. A video for the song was released on March 22, 2017, directed by Miles and AJ. Eilish released "Bored" on March 30, 2017, as part of the soundtrack to the Netflix series 13 Reasons Why. A video for "Bored" was released on June 26, 2017. In March of the same year, Apple Music showcased Eilish at the South by Southwest music festival. On June 30, 2017, Eilish released "Watch". Eilish released another single, "Copycat", on July 14, 2017, and announced the release of her debut EP, Don't Smile at Me. Eilish later released "Idontwannabeyouanymore" and "My Boy". On August 11, 2017, Eilish released Don't Smile at Me. The EP was a sleeper hit, reaching number 14 on the US Billboard 200. Eilish embarked on the Don't Smile at Me Tour throughout October 2017 in support of her EP. Eilish released "Bitches Broken Hearts" through SoundCloud on November 10, 2017.

Eilish's team worked with Spotify, which promoted her on its most popular playlist, "Today's Top Hits". The Baffler described Eilish's sound as fitting into the "streambait" genre consisting of largely "mid-tempo, melancholy pop" influenced by Lana Del Rey, whose "singing style, bleakness, and... hip-hop influenced production" shaped the aesthetic. Eilish's commercial success expanded with her Spotify promotion. In September 2017, Apple Music named Eilish their Up Next artist, which followed with a short documentary, a live session EP, and an interview with Zane Lowe on Apple Music's radio station Beats 1. That month, the live EP, Up Next Session: Billie Eilish, was released. On December 15, 2017, Eilish released her collaboration with American rapper Vince Staples, "&Burn", a remix of her single "Watch". It was included on the expanded edition of Don't Smile at Me.

In February 2018, Eilish embarked on her second headlining concert tour, the Where's My Mind Tour, which concluded in April 2018. "Bitches Broken Hearts" was re-released worldwide on March 30, 2018. For Record Store Day 2018, Eilish released "Party Favor" on a pink 7-inch vinyl, along with a cover of "Hotline Bling", by Drake, as the B-side. Eilish collaborated with American singer Khalid on the single "Lovely", which was released on April 19, 2018, and added to the soundtrack for the second season of 13 Reasons Why. She released "You Should See Me in a Crown" in July 2018. The same month, Eilish performed at the Mo Pop Festival.

On the day of release for her single "When the Party's Over", Eilish was featured in Vanity Fair's "73 Questions" rapid-fire questionnaire video series by Joe Sabia, who revisited an interview from October 2017. The resulting video was a side-by-side time capsule of both interviews showing her growth in popularity over one year. She signed a talent contract with Next Management for fashion and beauty endorsements in October 2018. She was placed on the 2018 Forbes 30 Under 30 list in November of that year, and released the single "Come Out and Play" in November 2018, which was written for a holiday-themed Apple Inc. commercial. In early January 2019, Don't Smile at Me reached 1 billion streams on Spotify, making her the youngest artist to top 1 billion streams on a project. That month, Eilish released "Bury a Friend" as the third single from her debut album When We All Fall Asleep, Where Do We Go?, along with "When I Was Older", a single inspired by the 2018 film Roma, which appeared on the compilation album Music Inspired by the Film Roma. In February, Eilish partnered with YouTube on a documentary miniseries, "A Snippet Into Billie's Mind". "Wish You Were Gay", her fourth single from the album, was released on March 4, 2019.

When We All Fall Asleep, Where Do We Go? was released on March 29, 2019. Spotify launched a "multi-level campaign behind the album", creating a multimedia playlist and "new product features" that Spotify said "allow for vertical video content, custom assets, and editorial storylines, all with the goal of creating more meaningful and engaging context for [Eilish's] fans." In Los Angeles, Spotify set up a "pop-up enhanced album experience", which included different artwork and a "multi-sensory" experience of each track for fans. The album debuted atop the Billboard 200 as well as on the UK Albums Chart, making Eilish the first artist born in the 2000s to have a number-one album in the US and the youngest female ever to have a number-one album in the United Kingdom. Upon the album's debut, Eilish broke the record for most simultaneously charting Hot 100 songs by a female artist, with 14, after every song from the album, excluding "Goodbye", charted on the Hot 100. The fifth single from the album, "Bad Guy", was released in conjunction with the album. A remix of the song featuring Justin Bieber was released in July 2019. In August, "Bad Guy" peaked at number-one in the US, ending Lil Nas X's record-breaking 19 weeks at number-one with "Old Town Road". She is the first artist born in the 2000s and the youngest artist since Lorde (with "Royals") to have a number-one single.

Eilish began her When We All Fall Asleep Tour at Coachella Festival in April 2019, with the tour concluding on November 17, 2019, in Mexico City. In August 2019, she partnered with Apple Music for Music Lab: Remix Billie Eilish, part of Apple Stores' Music Lab sessions during which fans deconstruct her song "You Should See Me In A Crown" and learn how to create their own remix on Apple devices and GarageBand. On September 27, 2019, Eilish announced her Where Do We Go? World Tour. The tour began in Miami on March 9, 2020, and ran for two more shows on March 10 in Orlando and March 12 in Raleigh before Eilish ended the tour prematurely due to the COVID-19 pandemic. The tour was set to conclude in Jakarta on September 7.

On November 7, 2019, Jack White's Third Man Records announced that the label would release an acoustic live album of Eilish's performance from the record label's Blue Room, exclusively sold on vinyl at Third Man retail locations in Nashville, Tennessee, and Detroit, Michigan. On November 13, 2019, she released her next single, "Everything I Wanted". 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 age 17, she became the youngest artist to be nominated in all four General Field categories. In the same month, Eilish was crowned 2019's Billboard Woman of the Year.

On January 14, 2020, Eilish was announced as performer of the title track for the 25th installment in the James Bond film franchise, No Time to Die, written and produced with her brother. With this announcement, Eilish became the youngest artist to write and perform a James Bond theme song. It became the second Bond theme song to top the British official charts and the first Bond theme performed by a female artist to do so. It was also Eilish's first number-one single in the UK. At the 62nd Annual Grammy Awards, she became the youngest person to win the four main Grammy categories – Best New Artist, Record of the Year, Song of the Year, and Album of the Year – in the same year. During the COVID-19 pandemic, Eilish and her brother performed for both iHeart Media's Living Room Concert for America, and Global Citizen's Together at Home concert series, singing a cover of Bobby Hebb's "Sunny" for the latter. Both virtual concerts were an effort to raise awareness and funds towards fighting the disease. On April 10, 2020, "Ilomilo" was sent to Italian contemporary hit radio stations by Universal Music Group, as When We All Fall Asleep, Where Do We Go?'s seventh and final single. On July 30, 2020, Eilish released "My Future", her first original release since "No Time to Die", along with an animated video. In 2020, she became the youngest person to feature on the Forbes Celebrity 100 list, with earnings of $53 million. In September 2020, Eilish released a collection of branded ukuleles with guitar manufacturer Fender.

On October 7, 2020, Eilish announced a virtual concert titled Where Do We Go? The Livestream. Staged in Los Angeles on October 24, the performance utilised extended reality (XR) technology and featured drummer Andrew Marshall and Eilish's brother, Finneas. Ticket proceeds were used to support touring crew members affected by COVID-19 cancellations via Crew Nation. In a Vanity Fair interview, Eilish said she was working on "sixteen new songs and lov[ing] them all", revealing an upcoming musical project. Eilish won three Billboard Music Awards on October 24—Top Female Artist, Top Billboard 200 Album (When We All Fall Asleep, Where Do We Go?), and Top New Artist—out of the 12 that she was nominated for. Also that month, she announced a new single, "Therefore I Am", which was released along with its video on November 12, 2020. Eilish performed "Therefore I Am" and "My Future" at the Jingle Ball in December 2020.

"Lo Vas a Olvidar", a single featuring Rosalía as part of HBO's Euphoria soundtrack, was released in January 2021, for the special "Fuck Anyone Who's Not a Sea Blob". On February 26, 2021, the R. J. Cutler-directed documentary film Billie Eilish: The World's a Little Blurry was released on Apple TV+ and in select movie theaters. The film was praised by critics and fans for its in-depth look at Eilish's personal life during her ascent to fame. At the 63rd Annual Grammy Awards, Eilish took home two awards: Best Song Written for Visual Media for her Bond theme and Record of the Year for "Everything I Wanted". In her acceptance speech for Record of the Year, Eilish said that Megan Thee Stallion "deserved to win", but still thanked her fans and her brother for her award. In 2021, she published her personally selected comprehensive book of photographs that shared "an intimate window into her life" on and off stage, By – Billie Eilish.

On April 27, 2021, Eilish announced on her Instagram account that her second album, Happier Than Ever, would be released on July 30, and the tracklist was made available on Apple Music. The album was released in various formats, including collectible vinyl and cassette colors. The album's release was preceded by five singles: "My Future", "Therefore I Am", "Your Power", "Lost Cause", and "NDA", and was accompanied by the title track. On December 2, 2021, Eilish announced an eco-friendly limited-edition vinyl version of Happier Than Ever made from recycled vinyl scraps. The collector's item was available only at a number of Gucci stores around the world and included Gucci-branded nail stickers designed by the brand's creative director, Alessandro Michele. To further promote the album, Eilish worked with Disney+ on the concert film Happier Than Ever: A Love Letter to Los Angeles, released in September 2021, and embarked on the Happier Than Ever, The World Tour in February 2022, concluding it in April 2023.

In June 2021, Eilish was criticized online for videos in which she mouthed the anti-Asian slur "chink" while lip-syncing the song "Fish" by Tyler, the Creator, while Matthew Tyler Vorce, her reported boyfriend at the time, received criticism for alleged social media posts in which he used offensive language and slurs against gay and Black people. Eilish was also accused of queerbaiting after using the caption "I love girls" to promote the music video for "Lost Cause". On June 22, she posted an apology to Instagram stories for her usage of "chink", saying that she was "appalled and embarrassed" by the video and that she was "13 or 14" at the time and did not know the slur was a derogatory term. She also addressed a separate video of what was viewed as her mocking an Asian accent, writing that she was actually "speaking in a silly gibberish made up voice". Reflecting on the events in a July 2021 interview, Eilish said: "I said so many things then that I totally don't agree with now, or think the opposite thing. The weirdest thing is how nothing ever goes away once it's on the internet ... When you're a fucking teenager, you don't really know yourself ... I didn't actually know how I really felt. So I just came up with this facade that I stuck to."

Eilish started formulating ideas for her third studio album's songs with Finneas in December 2021. In a July 2022 interview with Zane Lowe for Apple Music, she said she hoped to start writing the album in 2023. In 2022, Eilish won the Academy Award for Best Original Song for the song "No Time to Die" from the film No Time to Die, becoming the first person born in the 21st century to win an Academy Award. That same year, she became the youngest headliner to date for two festivals, specifically Glastonbury and Coachella. The Pixar film Turning Red was released that year, for which she and Finneas wrote three songs, "Nobody Like U", "U Know What's Up" and "1 True Love", performed by Turning Red's fictional boy band 4*Town.

In June 2022, during her world tour's Manchester show, Eilish debuted the then-unreleased ballad "TV". The song references the overturning of Roe v. Wade, a case that made abortion a constitutional right in the US. The next month, on July 21, she surprise-released the two-track EP Guitar Songs, which includes "TV" alongside "The 30th". Eilish explained her decision to surprise-release the EP during the interview with Lowe. She told him that while work on her third studio album was coming soon, she refused to wait until that time to put "TV" and "The 30th" on a track list. She wanted to spread their messages to her fans as soon as possible, noting the immediacy of its lyrics: "These songs are really current for me, and they're songs that I want to have said right now." Another reason was Eilish had grown tired of doing heavy, traditional promotion for upcoming music. She wanted to release songs like she had early in her career, previewing them for fans in live concerts before releasing them without much marketing.

Eilish worked with Apple Music to exclusively host a film of one of the Happier Than Ever tour concerts, specifically one of her shows at The O2 Arena in London. She billed the film as a way for fans who missed out on tickets to experience the tour, wanting more people to recognize her showmanship live. Three concerts, titled Happier Than Ever, The Hometown Encore, were held at the Kia Forum in Inglewood, California, from December 13 to 16, 2022, as part of the tour.

In 2023, Eilish made her acting debut in the Amazon Prime Video satirical thriller series Swarm. She starred as Eva, the leader of a cult inspired by NXIVM, and received positive reviews for her performance. Eilish wrote the song "What Was I Made For?" for the soundtrack of the 2023 film Barbie. According to statements posted on her social media, she was inspired to write the song after seeing unfinished scenes of the movie during its production. In 2024, the song won the Academy Award for Best Original Song and two Grammy Awards for Song of the Year and Best Song Written for Visual Media. It became the tenth song in history to win both an Academy Award for Best Original Song and a Grammy Award for Song of the Year, and Eilish became the youngest person ever to win two Academy Awards in any category.

On April 8, 2024, Eilish announced her third studio album, Hit Me Hard and Soft, which was released on May 17, 2024. She announced a tour to support the album, Hit Me Hard and Soft: The Tour, on April 29, 2024, with concerts in North America, Oceania and Europe between September 2024 and July 2025. Also in April, Eilish was announced to be the next "featured artist" inside the Fortnite spin-off game Fortnite Festival, along with an unlockable outfit in the game. While on a visit to London due to the success of the recently released album in the UK, Eilish appeared alongside London-based content creator Amelia Dimoldenberg on her web series Chicken Shop Date, which was dubbed as the "flirtiest episode yet", and also appeared as a guest host for children's channel CBeebies' bedtime story. In August, Eilish featured on a remix of Charli XCX's "Guess", a song from the deluxe version of the latter's album Brat, accompanied by a video containing scenes of Eilish in a bulldozer and the pair surrounded by piles of women's underwear, which were donated to the charity I Support the Girls. On August 11, 2024, Eilish performed "Birds of a Feather" on Belmont Shore, Long Beach, during the 2024 Summer Olympics closing ceremony as part of the handover to Los Angeles, which would host the Games in 2028.

In March 2026, it was reported that Eilish was in "advanced talks" to make her film acting debut as lead character Esther Greenwood in a Sarah Polley-directed adaptation of Sylvia Plath's The Bell Jar. Eilish's Hit Me Hard and Soft: The Tour (Live in 3D) concert film, which she co-directed and produced with James Cameron, was theatrically released on May 8, 2026.

Eilish grew up listening to the Beatles, Justin Bieber, Green Day, the 1975, Arctic Monkeys, Nine Inch Nails, Linkin Park and Lana Del Rey. She has named the Beatles as her greatest musical inspiration, crediting the band for inspiring "95% of [her] love for music". She has said that stumbling upon Aurora's "Runaway" on YouTube inspired her to pursue a music career. Hip hop is her favorite genre of music.

She has recounted that Matty Healy was an early inspiration for her: "His show is the second show I ever went to in my life. He changed so much about who I am, how I write music." She has also cited Tyler, the Creator, Childish Gambino, and Avril Lavigne as major musical and style influences. Other influences include Adele, Earl Sweatshirt, James Blake, Amy Winehouse, the Spice Girls, Lorde, Marina, Britney Spears, Nicki Minaj, XXXTentacion, and Twenty One Pilots. She has also shown appreciation for Paramore after inviting Hayley Williams to join her set during Williams's first Coachella set to perform an acoustic version of "Misery Business" and sing "Happier Than Ever". Eilish also named Rihanna as an inspiration for her style choices after she called fashion her "defense mechanism" during an acceptance speech. She has also credited Damon Albarn for changing the way she views art and music creation.

Eilish has been compared in the media to Lavigne, Lorde and Del Rey, the last of whom she says she does not want to be compared to, saying, "That woman has made her brand so perfect for her whole career and she shouldn't have to hear that." Eilish said that Ariana Grande's 2019 album Thank U, Next inspired her to continue making music.

Eilish lived with her parents in the Highland Park neighborhood of Los Angeles until 2019, when she moved out. She said she received a diagnosis of Tourette syndrome when she was 11 years old. She also has synesthesia and experienced depression. Eilish has also shared that she experienced sexual abuse as a child. She was raised vegetarian before becoming vegan.

Eilish prefers to keep her sexuality and personal relationships private, but is attracted to both men and women. From 2018 to 2019, she dated rapper Brandon Adams, who goes by the stage name 7:AMP. Eilish then dated actor Matthew Tyler Vorce from 2021 until 2022. She dated singer Jesse Rutherford from October 2022 to May 2023. Since 2025, Eilish has been in a relationship with Nat Wolff.

On a 2020 episode of the me and dad radio podcast, Eilish said: "When I was a little kid, I was super religious for no damn reason. My family never was religious. I didn't know anyone that was religious. And for some reason, as a little girl, I just was incredibly religious ... And then at one point, I don't know what happened. It just completely went away...[and I became] almost anti-religious for no reason." She said the experience made her more "open-minded" to other religions. Of her own religion, Eilish said: "I don't not believe and I don't do believe. I'm in a very neutral position. I'm open to every belief pretty much...[I love] the idea that there's a God. So why not? How would I know? I'm not going to say I know. I don't. Nobody knows."