Britney Spears is the defining figure of the Y2K pop era, the artist who shaped the sound and look of pop music in the first decade of the 21st century. Like Madonna before her, Spears melded her music to her image so thoroughly, it became impossible to separate the two: the title of "...Baby One More Time," her 1999 breakthrough hit, evokes the industrial Max Martin-produced hook and Spears' schoolgirl dance routine in equal measure. "...Baby One More Time" arrived in early 1999, months after the launch of MTV's Total Request Live and just as the pop charts were shaking off post-alternative doldrums in preparation for millennial bacchanalia that was just around the corner. Spears provided the soundtrack for that era as she moved from fizzy bubblegum like "(You Drive Me) Crazy" to the slinkier, sexier funk of "I'm a Slave 4 U." Hits were certainly central to Spears' appeal but she didn't reach the Billboard Top Ten with the same regularity as her fellow Mickey Mouse Club veterans Justin Timberlake, who fronted the boy band *NSYNC, and Christina Aguilera. Spears' stardom transcended the confines of the charts and even film, television, and the tabloids. Her cultural omnipresence in the 2000s elevated her to iconic status, turning her into the embodiment of all of that decade's glorious excesses. Spears' presence as a pop idol endured even after her personal problems led to her being placed in a conservatorship in 2008. In the years that followed, she continued to work, appearing as a judge on The X Factor, releasing singles that brought her back to the top of the charts and settling into a series of Las Vegas residencies.

Britney Jean Spears was born December 2, 1981, in the small town of Kentwood, Louisiana, and began singing and dancing at a young age. With a nationally televised appearance on Star Search already under her belt, Spears auditioned for the Disney Channel's The New Mickey Mouse Club at age eight. The producers turned her down as she was too young, but one of them took an interest and introduced her to an agent in New York. Spears spent the next three years studying at the Professional Performing Arts School, and also appeared in several television commercials and off-Broadway plays. At 11, she returned to The New Mickey Mouse Club for a second audition, and this time made the cut. Although her fellow Mouseketeers included an impressive array of future stars -- *NSYNC's Justin Timberlake and JC Chasez, Christina Aguilera, and Felicity actress Keri Russell -- the show was canceled after Spears' second season. She returned to New York at age 15 and set about auditioning for pop bands and recording demo tapes, one of which eventually landed her a deal with Jive Records.

Spears entered the studio with top writer/producers like Eric Foster White (Boyzone, Whitney Houston, Backstreet Boys) and Max Martin (Ace of Base, Backstreet Boys, *NSYNC). In late 1998, Jive released her debut single, the Martin-penned "...Baby One More Time." Powered by its video, in which Spears and a troupe of dancers were dressed as Catholic school jailbait, the single shot to the top of the Billboard charts. When Spears' debut album of the same title was released in early 1999, it entered the charts at number one and stayed there for six weeks. Once the ubiquitous lead single died down, the album kept spinning off hits: the Top Ten "(You Drive Me) Crazy," the near-Top 20 ballad "Sometimes," and the Top 20 "From the Bottom of My Broken Heart." By the end of 1999, ...Baby One More Time had sold ten million copies and went on to sell a good three-plus-million more on top of that. Its success touched off a wave of young pop divas who included Christina Aguilera, P!nk, Jessica Simpson, and Mandy Moore. Spears was a superstar.

By the time ...Baby One More Time finally started to lose steam on the singles and album charts, Spears was ready to release her follow-up. Oops!...I Did It Again appeared in the spring of 2000, and the title track was an instant smash, racing into the Top Ten. The album itself entered the charts at number one and sold over a million copies in its first week of release, setting a new record for single-week sales by a female artist. Follow-up singles included "Lucky," the gold-selling "Stronger," and "Don't Let Me Be the Last to Know," which was co-written by country diva Shania Twain and her producer Mutt Lange. A year after its release, Oops!...I Did It Again had sold over nine million copies. Rumors that Spears was dating *NSYNC heartthrob (and fellow ex-Mouseketeer) Justin Timberlake were eventually confirmed, which only added to the media attention lavished upon her.

For her next album, Spears looked ahead to a not-so-distant future when both she and much of her audience would be growing up. Released in late 2001, Britney tried to present the singer as a more mature young woman, and was accompanied by mild hints that her personal life wasn't always completely puritanical. It became her third straight album to debut at number one, although this time around the singles weren't as successful; "I'm a Slave 4 U," "I'm Not a Girl, Not Yet a Woman," and "Overprotected" all missed the Top Ten. In early 2002, Spears' feature-film debut, Crossroads, hit theaters, but its commercial performance was somewhat disappointing; moreover, her romance with Timberlake fizzled out not long after. Spears next made a cameo appearance in Mike Myers' Austin Powers: Goldmember, and contributed a remix of "Boys" to the soundtrack. Meanwhile, sales of Britney stalled at four million copies, perhaps in part because a new breed of teenage female singer/songwriters, like Michelle Branch and Avril Lavigne, was emerging as an alternative to the highly packaged teen queens. Spears took a break from recording and performing for several months, and began work on a new album in early 2003. The results, In the Zone, reflected a wish to be taken seriously as a mature (though still highly sexualized) adult. Predictably, it topped the charts and launched several singles into orbit, including the musically adventurous "Toxic," "Everytime," and "Me Against the Music."

In the Zone hit number one on the Billboard 200, and "Toxic" snagged a Grammy for Best Dance Recording, but in 2004 Britney's personal life started to hit the tabloids on a regular basis. She had a brief two-day marriage to childhood friend Jason Alexander, followed by the controversial Onyx Hotel tour, which was eventually canceled despite positive financial numbers. Soon, Britney revealed her relationship with her former backup dancer Kevin Federline. Spears and Federline married in September and were tabloid regulars in the months after the ceremony; some of this relationship was documented in Chaotic, a UPN reality show consisting mostly of their own home videos.

The year 2005 was no less eventful for Spears. She released Greatest Hits: My Prerogative that January, but it was the announcement of her pregnancy that really garnered the headlines. Her son Sean was born in September, and a bidding war ensued for first rights to the baby photos. As the hubbub surrounding Sean's birth continued, Britney released a remix album just in time for the holiday season. In 2006, Spears discovered she was pregnant again; shortly after the birth of her second son, Jayden, she divorced Federline. Following another headline-grabbing incident in early 2007 (in which Spears spontaneously shaved her head at a salon in Tarzana, California, much to the delight of nearby photographers), Spears sought help at Malibu's Promises Treatment Center. After leaving the facility, she began working on her comeback album and performed a few small shows at House of Blues locations in Los Angeles, San Diego, Anaheim, and Las Vegas that May. Despite ongoing turmoil in her life that summer and fall, Blackout arrived in October 2007. It proved to be her least successful album to date, charting three Top 40 hits but failing to achieve platinum certification within its first year of release.

Spears was dealt more blows in early 2008 when she lost custody of her children, made several court appearances, and was placed on involuntary psychiatric hold twice in one month. Blackout nevertheless won several MTV-sponsored awards, including Album of the Year from the Europe Music Awards in November 2008. That same fall, "Womanizer," the lead-off single from Spears' next record, became her first number one single in nearly a decade. The full-length Circus arrived in December, featuring a mix of syrupy ballads and uptempo dance numbers that were designed to fuel Spears' comeback. In 2009, the single "3" followed "Womanizer" to the top, and appeared on her career-spanning compilation The Singles Collection. In 2011, Spears returned with the studio album Femme Fatale, featuring the single "Hold It Against Me," which became her fourth single to top the Billboard Hot 100. The second single, the Ke$ha co-written "'Til the World Ends," didn't top the charts but it was a bigger hit, going double platinum in the U.S.

Britney supported Femme Fatale with an international tour that ran until the end of 2011; at the end of the year, the home video Live: The Femme Fatale Tour was released. Spears made a splashy return to television in 2012 when she signed to be one of the celebrity judges on the second season of the U.S. version of Simon Cowell's The X Factor. The show returned in the fall of 2012. Spears did not return to the show for its third season. Also in 2012, Britney appeared on will.i.am's track "Scream and Shout." This was the beginning of a greater partnership, as will.i.am wound up as the executive producer for her eighth studio album, Britney Jean. Preceded by the single "Work Bitch" -- along with a Britney cameo on Miley Cyrus' 2013 album Bangerz and the announcement of a two-year residency in Las Vegas -- Britney Jean appeared during the first week of December 2013. Although Britney Jean debuted in the Top Five on the Billboard 200, it would be her lowest-performing album to date. In the following years, she continued her Vegas residency and contributed to a pair of new tracks: "Pretty Girls" with Iggy Azalea and a cover of Suzanne Vega's "Tom's Diner" for Giorgio Moroder.

Spears released "Make Me," a midtempo track featuring rapper G-Eazy, in July 2016, with the full-length Glory appearing a month later. Glory peaked at three in the U.S., two in the U.K., and wound up generating only one other charting single, "Slumber Party," which peaked at 86. Spears supported Glory by taking her Vegas show on the road in 2017. Her Britney: Piece of Me production wrapped in Las Vegas at the end of 2017 and there were plans for another residency called Britney: Domination for February 2019, but it was canceled after her father suffered serious health problems. Spears entered an "indefinite work hiatus" that lasted into 2021, a period punctuated by a deluxe version of Glory in 2020. ~ Stephen Thomas Erlewine & Steve Huey, Rovi