After returning to the US, Spears toured shopping malls as part of her L'Oreal Hair Zone Mall Tour to promote her upcoming debut album. Her show was a four-song set, and she was accompanied by two backup dancers. Her first concert tour followed, as an opening act for NSYNC. Jive released her debut album ...Baby One More Time in January 1999. It debuted at number one on Billboard 200 and was certified two-times platinum by the Recording Industry Association of America (RIAA) after a month. The album topped the charts in fifteen countries and sold over 10 million copies in a year. It became the biggest-selling album ever by a teenage artist.

"...Baby One More Time" was released as the lead single from the album in September 1998. Jive originally wanted the associated music video to be animated, but Spears instead suggested the final concept of a Catholic schoolgirl. The single peaked at number one on the Billboard Hot 100, topping the chart for two consecutive weeks in January–February 1999. It sold more than 10 million copies, making it one of the best-selling singles in history. "...Baby One More Time" later received a Grammy nomination for Best Female Pop Vocal Performance. The title track also topped the singles chart for two weeks in the UK and became the fastest-selling single ever by a female artist, shipping over 460,000 copies. It would later become the 25th-most successful song in British chart history. Spears is the youngest female artist to have a million seller in the UK. The album's third single, "(You Drive Me) Crazy", became a top-ten hit worldwide and further propelled the success of the ...Baby One More Time album; the single would later appear in the John Schultz film Drive Me Crazy that year. The album has sold 30 million copies worldwide, making it one of the best-selling albums of all time. It is the best-selling debut album by any artist.

In June 1999, Spears began her first headlining ...Baby One More Time Tour in North America, which was positively received by critics. It also generated some controversy due to her racy outfits. An extension of the tour, titled (You Drive Me) Crazy Tour, followed in March 2000. Spears premiered songs from her upcoming second album during the show.

Oops!... I Did It Again, Spears's second Jive album, was released in May 2000. It debuted at number one in the US, selling 1.3 million copies, breaking the Nielsen SoundScan record for the highest debut sales by any solo artist. It has sold over 20 million copies worldwide to date, making it one of the best-selling albums of all time. Rob Sheffield of Rolling Stone said that "the great thing about Oops! – under the cheese surface, Britney's demand for satisfaction is complex, fierce and downright scary, making her a true child of rock & roll tradition". The album's lead single, "Oops!... I Did It Again", peaked at the top of the charts in Australia, New Zealand, the United Kingdom, and many other European nations, while the second single, "Lucky", peaked at number one in Austria, Germany, Sweden, and Switzerland. The album, as well as the title track, received Grammy nominations for Best Pop Vocal Album and Best Female Pop Vocal Performance, respectively.

The same year, Spears embarked on the Oops!... I Did It Again Tour, which grossed $40.9 million; she also published her first memoir, Britney Spears' Heart to Heart, written with her mother. On September 7, 2000, Spears performed at the 2000 MTV Video Music Awards. Halfway through the performance, she removed her black suit to reveal a sequined flesh-colored bodysuit, followed by a heavy dance routine. It is noted by critics as the moment that Spears showed signs of becoming a more provocative performer. Amidst media speculation, Spears confirmed she was dating NSYNC member Justin Timberlake. Spears and Timberlake both graduated via distance learning from the University of Nebraska High School. She also bought a home in Destin, Florida. In her 2023 memoir, Spears revealed that she had an abortion in late 2000 while dating Timberlake after he said they were not prepared for parenthood. Spears called the abortion "one of the most agonizing things I have ever experienced".

In January 2001, Spears hosted the 28th Annual American Music Awards, starred at Rock in Rio alongside NSYNC, and performed as a special guest in the Super Bowl XXXV halftime show headlined by Aerosmith and NSYNC. In February 2001, she signed a $7–8 million promotional deal with Pepsi and released another book co-written with her mother, A Mother's Gift. Her third studio album, Britney, was released in November 2001, with a funkier sound inspired by hip-hop artists such as Jay-Z and the Neptunes. Britney debuted at number one on the Billboard 200 and reached top five positions in Australia, the UK, and mainland Europe, and has sold 10 million copies worldwide.

Stephen Thomas Erlewine of AllMusic called Britney "the record where she strives to deepen her persona, making it more adult while still recognizably Britney. [...] it does sound like the work of a star who has now found and refined her voice, resulting in her best record yet". It was nominated for the Grammy Awards for Best Pop Vocal Album and Best Female Pop Vocal Performance for "Overprotected", and in 2007 it was named one of the best albums of the preceding 25 years by Entertainment Weekly. The lead single, "I'm a Slave 4 U", became a top-ten hit in several countries.

Spears's performance of the single at the 2001 MTV Video Music Awards featured a caged tiger (wrangled by Bhagavan Antle) and a large albino python draped over her shoulders. It was harshly received by animal rights organization PETA, who claimed the animals were mistreated and scrapped plans for an anti-fur billboard that was to feature Spears. Jocelyn Vena of MTV News summarized Spears's performance: "Draping herself in a white python and slithering around a steamy garden setting – surrounded by dancers in zebra and tiger outfits – Spears created one of the most striking visuals in the 27-year history of the show."

To support the album, Spears began the Dream Within a Dream Tour. The show was critically praised for its technical innovations, the pièce de résistance being a water screen that pumped two tons of water into the stage. The tour grossed $53.3 million, becoming the second highest-grossing tour of 2002 by a female artist, behind Cher's Farewell Tour. Her career success was highlighted by Forbes in 2002, as Spears was ranked the world's most powerful celebrity. Spears also landed her first starring role in Crossroads, released in February 2002. Although the film was largely panned, critics praised Spears's acting. The film was a box office success, grossing over $61.1 million worldwide on a $12 million budget.

In June 2002, Spears opened her first restaurant, Nyla, in New York City, but terminated her relationship in November due to mismanagement and "management's failure to keep her fully apprised". The following month, Spears announced she would take a six-month break from her career; however, she went back into the studio in November to record her new album. Spears's relationship with Justin Timberlake ended after three years. In November 2002, Timberlake released the song "Cry Me a River". Its music video featured a Spears look-alike and fueled rumors that she had been engaging in an affair, fueled by further rumors of possible relationships involving Timberlake's choreographer Wade Robson and Limp Bizkit's frontman Fred Durst. Spears had initially denied the allegations of a possible affair involving Durst, despite the two being spotted together on multiple occasions, even claiming the two had a friendly connection. In 2023, she admitted to an affair with Robson. As a response, Spears wrote the ballad "Everytime" with her backing vocalist and friend Annet Artani.

In August 2003, Spears opened the MTV Video Music Awards with Christina Aguilera, performing "Like a Virgin". Halfway through, they were joined by Madonna, whom they both kissed. The incident was highly publicized. In 2008, MTV listed the performance as the number-one opening moment in the history of the MTV Video Music Awards, while Blender cited it as one of the 25 sexiest music moments in television history.

Spears released her fourth studio album, In the Zone, in November 2003. She assumed more creative control by writing and co-producing most of the material. Vibe called it "a supremely confident dance record that also illustrates Spears's development as a songwriter". NPR named it one of the most important recordings of the decade, writing that "the decade's history of impeccably crafted pop is written on her body of work". In the Zone sold over 609,000 copies during its first week of availability in the United States, debuting at the top of the charts, making Spears the first female artist in the SoundScan era to have her first four studio albums debut at number one. It also debuted at the top of the charts in France and in the top ten in Belgium, Denmark, Sweden, and the Netherlands. The album produced four singles: "Me Against the Music", a collaboration with Madonna; "Toxic"—which won Spears her first Grammy for Best Dance Recording; "Everytime", and "Outrageous".

In January 2004, Spears married her childhood friend Jason Allen Alexander at A Little White Wedding Chapel in Las Vegas, Nevada. The marriage was annulled 55 hours later, following a petition to the court that stated that Spears "lacked understanding of her actions".

In March 2004, Spears embarked on the Onyx Hotel Tour in support of In the Zone. The tour was canceled in June 2004, when she fell and injured her left knee during the music video shoot for "Outrageous". She underwent arthroscopic surgery and wore a thigh brace for six weeks, followed by eight to twelve weeks of rehabilitation. That year, Spears became involved in the Kabbalah Centre through her friendship with Madonna.

In July 2004, Spears became engaged to struggling dancer Kevin Federline, whom she had met three months earlier. The romance was the subject of intense media attention, since Federline had recently broken up with actress Shar Jackson, who was still pregnant with their second child at the time. The stages of their relationship were chronicled in Spears's first reality show, Britney and Kevin: Chaotic, which premiered on May 17, 2005, on UPN. Spears later referred to the show in a 2013 interview as "probably the worst thing I've done in my career". They held a wedding ceremony on September 18, 2004, but were not legally married until three weeks later on October 6 due to a delay finalizing the couple's prenuptial agreement.

Shortly after, she released her first perfume, Curious, with Elizabeth Arden, which broke the company's first-week gross for a perfume. In October 2004, Spears took a career break to start a family. Greatest Hits: My Prerogative, her first greatest hits compilation album, was released in November 2004. Spears's cover version of Bobby Brown's "My Prerogative" was released as the lead single from the album, reaching the top of the charts in Finland, Ireland, Italy, and Norway. The second single, "Do Somethin'", was a top ten hit in Australia, the United Kingdom, and other countries of mainland Europe. In August 2005, Spears released "Someday (I Will Understand)", which was dedicated to her first son, who was born the following month. In November 2005, she released her first remix compilation, B in the Mix: The Remixes, which consists of 11 remixes.

In February 2006, pictures surfaced of Spears driving with her son on her lap instead of in a car seat. Child advocates were horrified by the photos of her holding the wheel with one hand and him with the other. Spears attributed the situation to a frightening encounter with paparazzi, and that it was a mistake on her part. The following month, she guest-starred on the Will & Grace episode "Buy, Buy Baby" as closeted lesbian Amber-Louise. She announced she no longer studied Kabbalah in May 2006, explaining, "my baby is my religion". Spears posed nude for the August 2006 cover of Harper's Bazaar; the photograph was compared to Demi Moore's 1991 Vanity Fair cover. In September 2006, her second son was born. Two months later, Spears filed for divorce from Federline, citing irreconcilable differences. Their divorce was finalized in July 2007, when the two reached a settlement and agreed to share joint custody of their sons.

Spears's maternal aunt, Sandra Bridges Covington, with whom she had been very close, died of ovarian cancer in January 2007. In February, Spears stayed in a drug rehabilitation facility in Antigua for less than a day. The following night, she shaved her head with electric clippers at a hair salon in Tarzana, Los Angeles. She admitted herself to other treatment facilities during the following weeks. In May 2007, she produced a series of promotional concerts at House of Blues venues, titled The M+M's Tour. In October 2007, Spears lost physical custody of her sons to Federline. The reasons for the court ruling were not revealed to the public. Spears was also sued by Louis Vuitton over her 2005 music video "Do Somethin'" for upholstering her Hummer interior in counterfeit Louis Vuitton cherry blossom fabric, which resulted in the video being banned on European TV stations.

In October 2007, Spears released her fifth studio album, Blackout. The album debuted atop the charts in Canada and Ireland, at number two in the US, France, Japan, Mexico, and the United Kingdom, and the top ten in Australia, South Korea, New Zealand, and many European nations. In the United States, it was Spears's first album not to debut at number one, although, she did become the only female artist to have her first five studio albums debut at the two top slots of the chart. The album received positive reviews from critics and had sold 3.1 million copies worldwide by the end of 2008. Blackout won Album of the Year at the 2008 MTV Europe Music Awards and was listed as the fifth Best Pop Album of the Decade by The Times.

Spears performed the lead single, "Gimme More", at the 2007 MTV Video Music Awards. The performance was widely panned by critics. Despite the criticism, the single enjoyed worldwide success, peaking at number one in Canada and within the top ten in almost every country it charted. The second single, "Piece of Me", reached the top of the charts in Ireland and reached the top five in Australia, Canada, Denmark, New Zealand, and the United Kingdom. The third single, "Break the Ice", was released the following year, and reached numbers seven and nine in Ireland and Canada, respectively. In December 2007, Spears began a relationship with paparazzo Adnan Ghalib.

In January 2008, after Spears refused to relinquish custody of her sons to Federline's representatives, she was institutionalized at Cedars-Sinai Medical Center due to her worsening mental condition. Her visitation rights were suspended at an emergency court hearing, and Federline was given sole custody. By the end of the month, she was put on a 5150 involuntary psychiatric hold at Ronald Reagan UCLA Medical Center. In February, her father Jamie filed a temporary conservatorship suit, granting him and attorney Andrew Wallet temporary control over her affairs. The following month, Spears guest-starred on the How I Met Your Mother episode "Ten Sessions" as a receptionist. Her performance drew positive reviews and brought the series its highest ratings ever. In July 2008, Spears regained some visitation rights after coming to an agreement with Federline.

In September 2008, Spears opened the MTV Video Music Awards with a pre-taped comedy sketch with Jonah Hill and an introduction speech. She won Best Female Video, Best Pop Video, and Video of the Year for "Piece of Me". A 60-minute introspective documentary, Britney: For the Record, was produced to chronicle Spears's return to the recording industry. Directed by Phil Griffin, For the Record was shot in Beverly Hills, Hollywood, and New York City during the third quarter of 2008. The documentary was broadcast on MTV to 5.6 million viewers for the two airings on the premiere night, December 1. It was the highest rating in its Sunday night time slot and in the network's history.

Spears's sixth studio album, Circus, was released in December 2008, two months after her conservatorship was extended indefinitely. It received positive reviews from critics and debuted at number one in Canada, the Czech Republic, and the United States, and within the top ten in many European nations. In the United States, Spears became the youngest female artist to have five albums debut at number one, earning a place in Guinness World Records. (Justin Bieber is the youngest male artist to do so, at age 18.) She also became the only act in the SoundScan era to have four albums debut with 500,000 or more copies sold. The album was one of the fastest-selling albums of the year and has sold 4 million copies worldwide. Its lead single, "Womanizer", became Spears's first chart-topper on the Billboard Hot 100 since "...Baby One More Time". The single also topped the charts in Belgium, Canada, Denmark, Finland, France, Norway, and Sweden. It was also nominated for the Grammy Award for Best Dance Recording.

In January 2009, Spears and Jamie obtained a restraining order against her former manager Sam Lutfi, ex-boyfriend Adnan Ghalib, and attorney Jon Eardley, who were accused of conspiring to gain control of Spears's affairs. Spears began the Circus Starring Britney Spears tour that March. With a gross of US $131.8 million, it became the fifth highest-grossing tour of the year. In November 2009, Spears released her second greatest hits album, The Singles Collection. The album's only single, "3", became her third number-one single in the US.

In May 2010, Spears's representatives confirmed she was dating her agent, Jason Trawick, and that they had decided to end their professional relationship to focus on their personal relationship. Spears designed a limited edition clothing line for Candie's, which was released in stores in July 2010. In September 2010, she made a cameo appearance on a Spears-themed tribute episode of the television series Glee, titled "Britney/Brittany". The episode drew the series's highest Nielsen rating so far in the 18–49 demographic.

In March 2011, Spears released her seventh studio album, Femme Fatale. The album peaked at number one in the United States, Canada, and Australia, and within the top ten on nearly every other chart. Its peak in the United States tied Spears with Mariah Carey and Janet Jackson for the third-most number ones among women. Femme Fatale has been certified platinum by the RIAA and, as of February 2014, had sold 2.4 million copies worldwide.

The album's lead single, "Hold It Against Me", debuted atop the Billboard Hot 100, becoming Spears's fourth number-one single on the chart and making her the second artist in history to have two consecutive singles debut at number one, after Mariah Carey. The second single, "Till the World Ends", peaked at number three on the Billboard Hot 100 in May, while the third single, "I Wanna Go", reached number seven in August. Femme Fatale became Spears's first album to have three of its songs reach the top ten on that chart. The fourth and final single, "Criminal", was released in September 2011. The music video sparked controversy when British politicians criticized Spears for using replica guns while filming the video in a London area that had been badly affected by the 2011 England riots. Spears's management briefly responded, stating, "The video is a fantasy story featuring Britney's boyfriend, Jason Trawick, which literally plays out the lyrics of a song written three years before the riots ever happened." In April 2011, Spears appeared in a remix of Rihanna's song "S&M". It reached number one in the US later that month, giving Spears her fifth number one on the chart. On Billboard's 2011 Year-End list, Spears was ranked number fourteen on the Artists of the Year, thirty-two on Billboard 200 artists, and ten on Billboard Hot 100 artists. Spears co-wrote "Whiplash", a song from the album When the Sun Goes Down (2011) by Selena Gomez & the Scene.

In June 2011, Spears embarked on her Femme Fatale Tour. The first ten dates of the tour grossed $6.2 million, and the tour peaked at number 55 on Pollstar's Top 100 North American Tours list for the halfway point of the year. The tour ended on December 10, 2011, in Puerto Rico, after 79 performances. A DVD of the tour was released in November 2011. In August 2011, Spears received the Michael Jackson Video Vanguard Award at the 2011 MTV Video Music Awards. The next month, she released her second remix album, B in the Mix: The Remixes Vol. 2. In December 2011, Spears became engaged to Trawick. Trawick was legally granted a role as co-conservator, alongside Jamie, in April 2012.

In May, Spears replaced Nicole Scherzinger as a judge for the second season of the American version of The X Factor, joining Simon Cowell, L.A. Reid, and fellow new judge Demi Lovato, who replaced Paula Abdul. With a reported salary of $15 million, she became the highest-paid judge on a singing competition series in television history. However, Katy Perry broke her record in 2018 after Perry was signed for a $25 million salary to serve as a judge on ABC's revival of American Idol. Spears mentored the Teens category; her final contestant, Carly Rose Sonenclar, was named the runner-up of the season. After Spears decided not to return, Paulina Rubio was hired as her permanent replacement for the show's third and final season.

That year, Spears collaborated with will.i.am on "Scream & Shout", released as the third single from his fourth studio album, #willpower (2013). The song later became Spears's sixth number-one single on the UK Singles Chart and peaked at number three on the Billboard Hot 100. "Scream & Shout" was among the best-selling songs of 2012 and 2013, with denoting sales of over 8.1 million worldwide. The accompanying music video was the third most-viewed in 2013 on Vevo, despite being released in 2012.[failed verification] In December 2012, Forbes named her music's top-earning woman of 2012, with estimated earnings of $58 million.

Spears began production on her eighth studio album, Britney Jean, in December 2012 and enlisted will.i.am as its executive producer in May 2013. In January 2013, Spears and Jason Trawick ended their engagement. Trawick was also removed as Spears's co-conservator, restoring her father as the sole conservator. Following the breakup, she began dating David Lucado in March; the couple split in August 2014. During the production of Britney Jean, Spears recorded the song "Ooh La La" for the soundtrack of The Smurfs 2, which was released in June 2013.

On September 17, 2013, she appeared on Good Morning America to announce her two-year concert residency at Planet Hollywood Resort & Casino in Las Vegas, titled Britney: Piece of Me. It began on December 27, 2013, and included a total of 100 shows throughout 2014 and 2015. During the same appearance, Spears announced that Britney Jean would be released on December 3, 2013, in the United States. It was released through RCA Records due to the disbandment of Jive Records in 2011, which had formed the joint RCA/Jive Label Group (initially known as BMG Label Group) between 2007 and 2011.

Britney Jean became Spears's final project under her original recording contract with Jive, which had guaranteed the release of eight studio albums. The record received a low amount of promotion and had little commercial impact, reportedly due to time conflicts involving preparations for Britney: Piece of Me. Upon its release, the record debuted at number four on the US Billboard 200 with first-week sales of 107,000 copies, becoming her lowest-peaking and lowest-selling album in the United States. It was also her lowest-charting and lowest-selling album in the UK, debuting at number 34 on the UK Albums Chart, selling 12,959 copies in its first week.

"Work Bitch" was released as the lead single from Britney Jean in September 2013. It debuted and peaked at number 12 on the US Billboard Hot 100, marking Spears's 31st entry on the chart, the fifth-highest debut of her career on the chart, and her seventh in the top 20. It also marked Spears's 19th top-20 entry and her 23rd top-40 single overall. It was her highest-sales debut since her 2011 number-one single "Hold It Against Me". "Work Bitch" debuted and peaked at number seven on the UK Singles Chart. The song also peaked within the top ten of the charts in Brazil, Canada, France, Italy, Mexico, and Spain.

The second single, "Perfume", premiered in November 2013. It debuted and peaked at number 76 on the US Billboard Hot 100. In October 2013, Spears was featured as a guest vocalist on the song "SMS (Bangerz)" by Miley Cyrus, from the latter's fourth studio album, Bangerz (2013). On January 8, 2014, Spears won Favorite Pop Artist at the 40th People's Choice Awards at the Microsoft Theater in Los Angeles. In August 2014, Spears confirmed she had renewed her contract with RCA and that she was writing and recording new music for her next album.

Spears announced via Twitter in August 2014 that she would be releasing an intimate apparel line called "The Intimate Britney Spears". It was available to be purchased beginning on September 9, 2014, in the United States and Canada through Spears's Intimate Collection website. It was available on September 25 for purchase in Europe. The company now ships to over 200 countries, including Australia and New Zealand. On September 25, 2014, Spears confirmed on Good Morning Britain that she extended her contract to perform her Britney: Piece of Me concert residency at Planet Hollywood Las Vegas for two additional years. Spears began dating television producer Charlie Ebersol in October 2014. The pair split in June 2015.

On May 14, 2015, Spears released a single, "Pretty Girls", with Iggy Azalea. It reached number 29 on the Billboard Hot 100. Spears and Azalea performed the track live at the 2015 Billboard Music Awards from The AXIS, the home of Spears's residency, to positive critical response. Entertainment Weekly praised the performance, noting "Spears gave one of her most energetic televised performances in years."

On June 16, 2015, Giorgio Moroder released the album Déjà Vu, which featured Spears on "Tom's Diner". The song was released as the fourth single from the album on October 9, 2015. In an interview, Moroder praised Spears's vocals and said she "sounds so good that you would hardly recognize her". At the 2015 Teen Choice Awards, Spears received the Candie's Style Icon Award, her ninth Teen Choice Award. In November 2015, Spears guest-starred as a fictionalized version of herself on the CW series Jane the Virgin. On the show, she danced to "Toxic" with Gina Rodriguez's character.

In November 2015, Spears confirmed via social media that she had begun recording her ninth studio album. On March 1, 2016, V announced that Spears would appear on the cover of its 100th issue, dated March 8, 2016, in addition to revealing three different covers shot by photographer Mario Testino for the milestone publication. The V editor-in-chief, Stephen Gan, said Spears was selected because of her status as an icon in the industry, and asked: "Who in our world did not grow up listening to her music?" In May 2016, Spears launched a casual role-play gaming application, Britney Spears: American Dream. The app, created by Glu Mobile, was made available through both iOS and Google Play.

On May 22, 2016, Spears performed a medley of her past singles at the 2016 Billboard Music Awards. In addition to opening the show, Spears was honored with the Billboard Millennium Award. On July 15, 2016, Spears released the lead single, "Make Me", from her forthcoming album, featuring guest vocals from American rapper G-Eazy. The album, Glory, was formally released on August 26, 2016. On August 16, 2016, MTV and Spears announced that she would perform at the 2016 MTV Video Music Awards. The performance marked Spears's first time returning to the VMA stage after her widely panned performance of "Gimme More" at the 2007 show nine years earlier. Along with "Make Me", Spears and G-Eazy also performed the latter's hit song "Me, Myself & I".

Spears appeared on the cover of Marie Claire UK for the October 2016 issue. In the publication, Spears revealed that she had suffered from crippling anxiety in the past, and that motherhood played a major role in helping her overcome it. "My boys don't care if everything isn't perfect. They don't judge me", Spears said in the issue. In November 2016, during an interview with Las Vegas Blog, Spears confirmed she had already begun work on her next album, stating: "I'm not sure what I want the next album to sound like... I just know that I'm excited to get into the studio again and actually have already been back recording." In the same month, she released a remix version of "Slumber Party" as the second single from Glory, featuring Tinashe.

She began dating "Slumber Party"'s music video co-star Sam Asghari after the two met on set. In January 2017, Spears received four wins out of four nominations at the 43rd People's Choice Awards, including Favorite Pop Artist, Female Artist, Social Media Celebrity, as well as Comedic Collaboration for a skit with Ellen DeGeneres for The Ellen DeGeneres Show. In March 2017, Spears announced that her residency concert would be performed abroad as a world tour, Britney: Live in Concert, with dates in select Asian cities. In April 2017, the Israeli Labor Party announced that it would reschedule its July primary election to avoid conflict with Spears's sold-out Tel Aviv concert, citing traffic and security concerns.

Spears's manager Larry Rudolph also announced the residency would not be extended following her contract expiration with Caesars Entertainment at the end of 2017. On April 29, 2017, Spears became the first recipient of the Icon Award at the 2017 Radio Disney Music Awards. On November 4, 2017, Spears attended the grand opening of the Nevada Childhood Cancer Foundation Britney Spears Campus in Las Vegas. Later that month, Forbes announced that Spears was the eighth-highest-earning female musician, earning $34 million in 2017. On December 31, 2017, Spears performed the final show of Britney: Piece of Me. The final performance reportedly brought in $1.172 million, setting a new box office record for a single show in Las Vegas, a record previously held by Jennifer Lopez. Performances of "Toxic" and "Work Bitch" were recorded on earlier dates and aired on ABC's Dick Clark's New Year's Rockin' Eve to a record audience of 25.6 million.

In January 2018, Spears released her 24th perfume with Elizabeth Arden, Sunset Fantasy, and announced the Piece of Me Tour, which took place in July 2018 in North America and Europe. Tickets were sold out within minutes for major cities, and additional dates were added to meet the demand. Pitbull was the supporting act for the European leg. The tour ranked at 86 in North America and 30 worldwide on Pollstar's 2018 Year-End Top 100 Tours chart. In total, the tour grossed $54.3 million, with 260,531 tickets sold, and was the sixth-highest-grossing female tour of 2018. It was also the United Kingdom's second-best-selling female tour of 2018.

On March 20, 2018, Spears was announced as part of a campaign for French luxury fashion house Kenzo. The company said it aimed to shake up the "jungle" world of fashion with Spears's "La Collection Memento No. 2" campaign. On April 12, 2018, Spears was honored with the 2018 GLAAD Vanguard Award at the GLAAD Media Awards for her role in "accelerating acceptance for the LGBTQ community". On April 27, 2018, Epic Rights announced a new partnership with Spears to debut her own fashion line in 2019, which would include clothing, fitness apparel, accessories, and electronics.

In July 2018, Spears released her first unisex fragrance, Prerogative. On October 18, 2018, Spears announced her second Las Vegas residency show, Britney: Domination, which was set to launch at Park MGM's Park Theatre on February 13, 2019. Spears was slated to make $507,000 per show, which would have made her the highest paid act on the Las Vegas Strip. On October 21, 2018, Spears performed at the Formula One Grand Prix in Austin, the final performance of her Piece of Me Tour.

By early 2019, Spears announced an indefinite hiatus and the cancellation of her Las Vegas residency after her father, Jamie, suffered a near-fatal colon rupture and Andrew Wallet resigned as co-conservator of her estate. Following allegations of Jamie's involvement in cancelling Spears's residency and placing her in a psychiatric facility, a movement titled #FreeBritney was organized in May 2019. Judge Brenda Penny announced a professional evaluation of the conservatorship that month. That September, Kevin Federline filed a restraining order against Jamie following an alleged physical altercation between Jamie and one of her sons.

An interactive pop-up museum dedicated to Spears, dubbed "The Zone", opened in Los Angeles in February 2020, though it was later suspended due to the COVID-19 pandemic. She released Glory's Japanese-exclusive bonus track, "Mood Ring" as a single, and debuted a new cover of the album to streaming and digital platforms worldwide in May 2020. In December, Spears released an updated deluxe edition of Glory, which includes "Mood Ring" and new songs "Swimming in the Stars" and "Matches", a collaboration with Backstreet Boys.

In February 2021, a television documentary titled Framing Britney Spears aired on FX. That June, The New York Times obtained confidential court documents stating that Spears had pushed for years to end her conservatorship. At the conservatorship hearing, Spears announced her intentions to terminate the conservatorship, citing abuse. In July, Bessemer Trust and Spears's longtime manager Larry Rudolph resigned. Later in the year, Spears announced her engagement to her longtime boyfriend, Sam Asghari. After Jamie filed a suit to end his involvement, Penny terminated Spears's conservatorship in November.

In April 2022, she announced her pregnancy with Asghari's child, which ended in a miscarriage the following month. The couple married on June 9 at her home in Thousand Oaks, Los Angeles. None of Spears's immediate family (including her parents, sister, and brother) were invited; her two sons did not attend. Spears's ex-husband, Jason Alexander, attempted to crash the wedding by breaking into her home, armed with a knife, but was arrested. A three-year restraining order was subsequently enacted. On August 26, Spears and English musician Elton John released the duet "Hold Me Closer", a remake of John's 1972 single "Tiny Dancer". It was Spears's first musical release since dissolving her conservatorship. "Hold Me Closer" debuted at number six on the US Billboard Hot 100, becoming her 14th top-ten single and her highest-charting song in the chart since "Scream & Shout" (2012). It debuted at number three on the UK Singles Chart, earning Spears her 24th top-ten.

Since her conservatorship's dissolution, Spears's personal life, social media presence, and overall well-being have been subject to renewed media interest and fan speculation, giving rise to conspiracy theories. On January 24, 2023, deputies from the Ventura County Sheriff's Office performed a welfare check at Spears's residence after receiving several calls from fans who were concerned after she deleted her Instagram account. A spokesperson for the Sheriff's Department stated that Spears "was safe and in no danger". Spears addressed the incident on her Twitter account, asking fans to respect her privacy. Spears and the rapper will.i.am released their single, "Mind Your Business", on July 21, 2023. On August 16, it was announced Spears and Asghari separated after 14 months of marriage. On May 1, 2024, they reached a divorce settlement. The following day, the judge signed off on the settlement and the couple were divorced on December 2, 2024. In September 2023, an additional welfare check was initiated when Spears posted an Instagram video of herself dancing with knives. Her security team assured the attending officer that there was no immediate threat to her safety, and the officer departed. Spears also clarified that the knives were not real.

After signing a $15 million book deal in February 2022 in one of the largest deals ever made, she published a second memoir, The Woman in Me, in October 2023. It details her rise to fame, public media events, her conservatorship, and her newfound freedom. In the United States, it sold 1.1 million copies, while worldwide it sold 2.4 million copies in print sales during its first week of release.

In January 2024, reports circulated that Charli XCX and Julia Michaels had been asked to write songs for Spears, and Rolling Stone reported that "management and A&R are trying to get her excited for the music". Spears denied the reports, saying she would never return to the music industry. However, she also said that she had written more than 20 songs for other artists in the previous two years. In May 2024, Charli XCX confirmed in an interview that she had indeed been asked to write for Spears, for which she traveled to Malibu, but that she did not know if Spears was involved, explaining that "the team were present... But she didn't record it. She obviously didn't."

In 2026, she clarified her exit from the music industry, saying that she would "never perform in the US again", but did not rule out performing elsewhere, saying "I hope to be ... performing with my son … in the UK and Australia very soon."

In February 2026, Variety reported that music publisher Primary Wave had acquired the rights to Spears' entire music catalog along with other rights. The BBC reported that the purchase took place on December 30, 2025, for roughly $200 million. The following month, she was arrested in Ventura County, California, on suspicion of driving under the influence. In April, Spears' representative stated that she had checked herself into a rehabilitation facility. On April 30, 2026, she would be officially given a criminal DUI charge. Spears was scheduled to appear in court for her arraignment hearing May 4, 2026. It had been agreed that Spears could avoid jail time for this charge if she pled guilty to reckless driving, for which she would only get probation and be required to both complete a DUI class and pay state-mandated fines and fees.

On April 30, 2026, Spears checked out of rehab. On May 4, 2026, Spears, who was absent from court during her arraignment hearing and had her defense attorney appear on her behalf, pled guilty in a Ventura County court to one count of reckless driving. She was then sentenced to one year of probation and one day in jail, with credit for the time in jail she served following her March 2026 arrest. In addition, Spears was ordered to meet with a psychologist once a week and a psychiatrist twice a month. She was also fined $571 and is required to attend a three-month DUI program which sees drivers complete 30 hours of class time. As part of her plea deal, Spears' vehicle became authorized to be searched for drugs and alcohol.

Spears has cited Madonna, Janet Jackson, and Whitney Houston as major influences, her "three favorite artists" as a child, whom she would "sing along to ... day and night in [her] living room"; Houston's "I Have Nothing" was the song she auditioned to that landed her record deal with Jive Records. Spears also named Mariah Carey as "one of the main reasons I started singing". Throughout her career, Spears has drawn frequent comparisons to Madonna and Jackson in particular, in terms of vocals, choreography, and stage presence. According to Spears: "I know when I was younger, I looked up to people ... like, you know, Janet Jackson and Madonna. And they were major inspirations for me. But I also had my own identity and I knew who I was."

In the 2002 book Madonnastyle by Carol Clerk, Spears is quoted saying: "I have been a huge fan of Madonna since I was a little girl. She's the person that I've really looked up to. I would really, really like to be a legend like Madonna." Spears cited "That's the Way Love Goes" as the inspiration for her song "Touch of My Hand" from her album In the Zone, saying "I like to compare it to 'That's the Way Love Goes,' kind of a Janet Jackson thing." She also said her song "Just Luv Me" from her Glory album also reminded her of "That's the Way Love Goes".

After personally meeting Spears, Jackson stated: "she said to me, 'I'm such a big fan; I really admire you.' That's so flattering. Everyone gets inspiration from some place. And it's awesome to see someone else coming up who's dancing and singing, and seeing how all these kids relate to her. A lot of people put it down, but what she does is a positive thing." Madonna said of Spears in the documentary Britney: For the Record: "I admire her talent as an artist ... There are aspects about her that I recognize in myself when I first started out in my career." Spears has also named Michael Jackson, Mariah Carey, Sheryl Crow, Otis Redding, Shania Twain, Brandy, Beyoncé, Natalie Imbruglia, Cher, and Prince as inspirations, and younger artists such as Selena Gomez and Ariana Grande.

Spears is described as a pop artist and generally explores the genre in the form of dance-pop. Following her debut, she was credited with influencing the revival of teen pop in the late 1990s. Rob Sheffield of Rolling Stone wrote: "Spears carries on the classic archetype of the rock & roll teen queen, the dungaree doll, the angel baby who just has to make a scene." In a review of ...Baby One More Time, Stephen Thomas Erlewine of AllMusic described her music as a "blend of infectious, rap-inflected dance-pop and smooth balladry". Oops!... I Did It Again saw Spears working with several R&B producers to create "a combination of bubblegum, urban soul, and raga". Her third studio album, Britney, derived from the teen pop niche "[r]hythmically and melodically", but was described as "sharper, tougher than what came before", incorporating genres such as R&B, disco, and funk.

Spears has explored and heavily incorporated the genres of electropop and dance music in her records, as well as influences of urban and hip-hop, which are most present on In the Zone and Blackout. In the Zone also experiments with Euro trance, reggae, and Middle Eastern music. Femme Fatale and Britney Jean were also heavily influenced by electronic music genres. Spears's ninth studio album, Glory, is more eclectic and experimental than her previously released work. She commented that it "took a lot of time ... it's really different ... there are like two or three songs that go in the direction of more urban that I've wanted to do for a long time now, and I just haven't really done that."

...Baby One More Time and Oops!... I Did It Again address themes such as love and relationships from a teenager's point of view. Following the massive commercial success of her first two studio albums, Spears's team and producers wanted to maintain the formula that took her to the top of the charts. Spears, however, was no longer satisfied with the sound and themes covered on her records. She co-wrote five songs and choose each track's producer on her third studio album, Britney, whose lyrics address the subjects of reaching adulthood, sexuality, and self-discovery. Sex, dancing, freedom, and love continued to be Spears's main subjects on her subsequent albums. Her fifth studio effort, Blackout, also addresses issues such as fame and media scrutiny, including on the song "Piece of Me".

Spears's music has also been noted for some catchphrases. The opening in her debut single "...Baby One More Time", "Oh, baby baby" is considered to be one of her signature lines and has been parodied in the media by various artists such as Nicole Scherzinger and Ariana Grande. It has been used in various forms throughout her music, such as simply, "baby" and "oh baby", as well as the Blackout track, "Ooh Ooh Baby". On the initial development of "...Baby One More Time", Barry Weiss noted Spears's inception of the catchphrase from her strange ad-libbing during the recording of the song. He commented further, "We thought it was really weird at first. It was strange. It was not the way Max wrote it. But it worked! We thought it could be a really good opening salvo for her." The opening line in "Gimme More", "It's Britney, bitch" has become another signature phrase. An early review of Blackout suggested the phrase was "simply laughable". Amy Roberts of Bustle called it "an indelible cultural turning point, transforming a frenetic, floundering moment in the superstar's career to one of strength and empowerment".

Referred to as the "Princess of Pop", Spears was credited as one of the "driving force[s] behind the return of teen pop in the late 1990s". Rolling Stone's Stacy Lambe explained that she "help[ed] to usher in a new era for the genre that had gone dormant in the decade that followed New Kids on the Block. ... Spears would lead an army of pop stars ... built on slick Max Martin productions, plenty of sexual innuendo and dance-heavy performances. [She became] one of the most successful artists of all time—and a cautionary tale for a generation, whether they paid attention or not." In a 2021 article for Time, Maura Johnston opined that "Spears's legacy as a pop artist is complex, made up of dazzling musical heights and music-business-borne lows". Johnston also commented: "While Spears's catalog is part of the canon that defines the first 20 years of this millennium, one hopes that her public struggles, and the strength she's shown while enduring them, will lead to her cementing her true legacy: Reshaping the machine that turns those songs into cultural touchstones."

Glamour contributor Christopher Rosa described her as "one of pop music's defining voices. ... When she emerged onto the scene in 1998 with ...Baby One More Time, the world hadn't seen a performer like her. Not since Madonna had a female artist affected the genre so profoundly." Billboard's Robert Kelly observed that Spears's "sexy and coy" vocals on her debut single "...Baby One More Time" "kicked off a new era of pop vocal stylings that would influence countless artists to come". In 2020, Rolling Stone ranked the song at number one on a list of the 100 Greatest Debut Singles of All Time and Rob Sheffield described it as "One of those pop manifestos that announces a new sound, a new era, a new century. But most of all, a new star ... With "...Baby One More Time", [Spears] changed the sound of pop forever: It's Britney, bitch. Nothing was ever the same."

Spears was at the forefront of the female teen pop explosion starting in 1999 and extending through the 2000s, leading the pack of Christina Aguilera, Jessica Simpson, and Mandy Moore. All of these performers had been developing material in 1998, but the market changed dramatically in December 1998 when Spears's single and video were charting highly. RCA Records quickly signed Aguilera and released her debut single to capitalize on Spears's success, producing her debut hit single "Genie in a Bottle". Simpson consciously modeled her persona as more mature than Spears; her "I Wanna Love You Forever" charted in September 1999, and her album Sweet Kisses followed shortly after. Moore's first single, "Candy", hit the airwaves a month before Simpson's single. Fueling media stories about their competition for first place, Spears and Aguilera traded barbs but also compliments through the 2000s.

Alim Kheraj of Dazed called Spears "one of pop's most important pioneers". After eighteen years as a performer, Billboard described her as having "earned her title as one of pop's reigning queens. Since her early days as a Mouseketeer, [Spears] has pushed the boundaries of 21st century sounds, paving the way for a generation of artists to shamelessly embrace glossy pop and redefine how one can accrue consistent success in the music industry." Entertainment Weekly's Adam Markovitz described Spears as "an American institution, as deeply sacred and messed up as pro wrestling or the filibuster." She was ranked at number six on Billboard's 2024 Greatest Pop Stars of the 21st Century list and number 14 on its 2025 "Top 100 Women Artists of the 21st Century" list.

Spears has been credited with redefining Las Vegas residencies as a retirement place for musicians. Her debut concert residency Britney: Piece of Me was described as "the natural evolution of Celine Dion's powerhourse Vegas residency, a still-charting star of another generation redefining the role of Strip headliner." Forbes named Spears the sixth-highest-earning female musician of 2015. She is credited with influencing and paving the way for other artists's residencies such as Jennifer Lopez's Jennifer Lopez: All I Have, Bruno Mars's Bruno Mars at Park MGM, and Backstreet Boys' Backstreet Boys: Larger Than Life. The arrival of Spears "saw the pop promoters finally tap into the younger crowd arriving in town for a good time".

Spears's much-publicized personal problems and her subsequent career comeback have inspired some artists. Gwyneth Paltrow's character in the 2010 film Country Strong was inspired by Spears's treatment by the media. According to film director Shana Fest, "that's where this movie came from. I mean, I was seeing what was happening in the media to Britney Spears. I think it's tragic how we treat people who give us so much, and we love to see them knocked down to build them back up again, to knock them down again." Nicki Minaj has cited Spears's comeback after her much-publicized personal issues as an inspiration. Spears's hounding by paparazzi and personal problems also inspired Barry Manilow's album 15 Minutes. Manilow said: "She couldn't have a life without them pulling up next to her car and following her and driving her crazy to the point where, that was around the time she shaved off her hair. ... We all looked at it in horror ... So it seemed like a thing to be writing an album about." Bebo Norman wrote a song about Spears, called "Britney", which was inspired by "culture's make-or-break treatment of celebrities". Along with Alicia Silverstone, Christy Turlington, and Naomi Campbell, Spears has been credited with introducing the navel piercing to mainstream culture.

After returning to the US, Spears toured shopping malls as part of her L'Oreal Hair Zone Mall Tour to promote her upcoming debut album. Her show was a four-song set, and she was accompanied by two backup dancers. Her first concert tour followed, as an opening act for NSYNC. Jive released her debut album ...Baby One More Time in January 1999. It debuted at number one on Billboard 200 and was certified two-times platinum by the Recording Industry Association of America (RIAA) after a month. The album topped the charts in fifteen countries and sold over 10 million copies in a year. It became the biggest-selling album ever by a teenage artist.

"...Baby One More Time" was released as the lead single from the album in September 1998. Jive originally wanted the associated music video to be animated, but Spears instead suggested the final concept of a Catholic schoolgirl. The single peaked at number one on the Billboard Hot 100, topping the chart for two consecutive weeks in January–February 1999. It sold more than 10 million copies, making it one of the best-selling singles in history. "...Baby One More Time" later received a Grammy nomination for Best Female Pop Vocal Performance. The title track also topped the singles chart for two weeks in the UK and became the fastest-selling single ever by a female artist, shipping over 460,000 copies. It would later become the 25th-most successful song in British chart history. Spears is the youngest female artist to have a million seller in the UK. The album's third single, "(You Drive Me) Crazy", became a top-ten hit worldwide and further propelled the success of the ...Baby One More Time album; the single would later appear in the John Schultz film Drive Me Crazy that year. The album has sold 30 million copies worldwide, making it one of the best-selling albums of all time. It is the best-selling debut album by any artist.

In June 1999, Spears began her first headlining ...Baby One More Time Tour in North America, which was positively received by critics. It also generated some controversy due to her racy outfits. An extension of the tour, titled (You Drive Me) Crazy Tour, followed in March 2000. Spears premiered songs from her upcoming second album during the show.

Oops!... I Did It Again, Spears's second Jive album, was released in May 2000. It debuted at number one in the US, selling 1.3 million copies, breaking the Nielsen SoundScan record for the highest debut sales by any solo artist. It has sold over 20 million copies worldwide to date, making it one of the best-selling albums of all time. Rob Sheffield of Rolling Stone said that "the great thing about Oops! – under the cheese surface, Britney's demand for satisfaction is complex, fierce and downright scary, making her a true child of rock & roll tradition". The album's lead single, "Oops!... I Did It Again", peaked at the top of the charts in Australia, New Zealand, the United Kingdom, and many other European nations, while the second single, "Lucky", peaked at number one in Austria, Germany, Sweden, and Switzerland. The album, as well as the title track, received Grammy nominations for Best Pop Vocal Album and Best Female Pop Vocal Performance, respectively.

The same year, Spears embarked on the Oops!... I Did It Again Tour, which grossed $40.9 million; she also published her first memoir, Britney Spears' Heart to Heart, written with her mother. On September 7, 2000, Spears performed at the 2000 MTV Video Music Awards. Halfway through the performance, she removed her black suit to reveal a sequined flesh-colored bodysuit, followed by a heavy dance routine. It is noted by critics as the moment that Spears showed signs of becoming a more provocative performer. Amidst media speculation, Spears confirmed she was dating NSYNC member Justin Timberlake. Spears and Timberlake both graduated via distance learning from the University of Nebraska High School. She also bought a home in Destin, Florida. In her 2023 memoir, Spears revealed that she had an abortion in late 2000 while dating Timberlake after he said they were not prepared for parenthood. Spears called the abortion "one of the most agonizing things I have ever experienced".

In January 2001, Spears hosted the 28th Annual American Music Awards, starred at Rock in Rio alongside NSYNC, and performed as a special guest in the Super Bowl XXXV halftime show headlined by Aerosmith and NSYNC. In February 2001, she signed a $7–8 million promotional deal with Pepsi and released another book co-written with her mother, A Mother's Gift. Her third studio album, Britney, was released in November 2001, with a funkier sound inspired by hip-hop artists such as Jay-Z and the Neptunes. Britney debuted at number one on the Billboard 200 and reached top five positions in Australia, the UK, and mainland Europe, and has sold 10 million copies worldwide.

Stephen Thomas Erlewine of AllMusic called Britney "the record where she strives to deepen her persona, making it more adult while still recognizably Britney. [...] it does sound like the work of a star who has now found and refined her voice, resulting in her best record yet". It was nominated for the Grammy Awards for Best Pop Vocal Album and Best Female Pop Vocal Performance for "Overprotected", and in 2007 it was named one of the best albums of the preceding 25 years by Entertainment Weekly. The lead single, "I'm a Slave 4 U", became a top-ten hit in several countries.

Spears's performance of the single at the 2001 MTV Video Music Awards featured a caged tiger (wrangled by Bhagavan Antle) and a large albino python draped over her shoulders. It was harshly received by animal rights organization PETA, who claimed the animals were mistreated and scrapped plans for an anti-fur billboard that was to feature Spears. Jocelyn Vena of MTV News summarized Spears's performance: "Draping herself in a white python and slithering around a steamy garden setting – surrounded by dancers in zebra and tiger outfits – Spears created one of the most striking visuals in the 27-year history of the show."

To support the album, Spears began the Dream Within a Dream Tour. The show was critically praised for its technical innovations, the pièce de résistance being a water screen that pumped two tons of water into the stage. The tour grossed $53.3 million, becoming the second highest-grossing tour of 2002 by a female artist, behind Cher's Farewell Tour. Her career success was highlighted by Forbes in 2002, as Spears was ranked the world's most powerful celebrity. Spears also landed her first starring role in Crossroads, released in February 2002. Although the film was largely panned, critics praised Spears's acting. The film was a box office success, grossing over $61.1 million worldwide on a $12 million budget.

In June 2002, Spears opened her first restaurant, Nyla, in New York City, but terminated her relationship in November due to mismanagement and "management's failure to keep her fully apprised". The following month, Spears announced she would take a six-month break from her career; however, she went back into the studio in November to record her new album. Spears's relationship with Justin Timberlake ended after three years. In November 2002, Timberlake released the song "Cry Me a River". Its music video featured a Spears look-alike and fueled rumors that she had been engaging in an affair, fueled by further rumors of possible relationships involving Timberlake's choreographer Wade Robson and Limp Bizkit's frontman Fred Durst. Spears had initially denied the allegations of a possible affair involving Durst, despite the two being spotted together on multiple occasions, even claiming the two had a friendly connection. In 2023, she admitted to an affair with Robson. As a response, Spears wrote the ballad "Everytime" with her backing vocalist and friend Annet Artani.

In August 2003, Spears opened the MTV Video Music Awards with Christina Aguilera, performing "Like a Virgin". Halfway through, they were joined by Madonna, whom they both kissed. The incident was highly publicized. In 2008, MTV listed the performance as the number-one opening moment in the history of the MTV Video Music Awards, while Blender cited it as one of the 25 sexiest music moments in television history.

Spears released her fourth studio album, In the Zone, in November 2003. She assumed more creative control by writing and co-producing most of the material. Vibe called it "a supremely confident dance record that also illustrates Spears's development as a songwriter". NPR named it one of the most important recordings of the decade, writing that "the decade's history of impeccably crafted pop is written on her body of work". In the Zone sold over 609,000 copies during its first week of availability in the United States, debuting at the top of the charts, making Spears the first female artist in the SoundScan era to have her first four studio albums debut at number one. It also debuted at the top of the charts in France and in the top ten in Belgium, Denmark, Sweden, and the Netherlands. The album produced four singles: "Me Against the Music", a collaboration with Madonna; "Toxic"—which won Spears her first Grammy for Best Dance Recording; "Everytime", and "Outrageous".

In January 2004, Spears married her childhood friend Jason Allen Alexander at A Little White Wedding Chapel in Las Vegas, Nevada. The marriage was annulled 55 hours later, following a petition to the court that stated that Spears "lacked understanding of her actions".

In March 2004, Spears embarked on the Onyx Hotel Tour in support of In the Zone. The tour was canceled in June 2004, when she fell and injured her left knee during the music video shoot for "Outrageous". She underwent arthroscopic surgery and wore a thigh brace for six weeks, followed by eight to twelve weeks of rehabilitation. That year, Spears became involved in the Kabbalah Centre through her friendship with Madonna.

In July 2004, Spears became engaged to struggling dancer Kevin Federline, whom she had met three months earlier. The romance was the subject of intense media attention, since Federline had recently broken up with actress Shar Jackson, who was still pregnant with their second child at the time. The stages of their relationship were chronicled in Spears's first reality show, Britney and Kevin: Chaotic, which premiered on May 17, 2005, on UPN. Spears later referred to the show in a 2013 interview as "probably the worst thing I've done in my career". They held a wedding ceremony on September 18, 2004, but were not legally married until three weeks later on October 6 due to a delay finalizing the couple's prenuptial agreement.

Shortly after, she released her first perfume, Curious, with Elizabeth Arden, which broke the company's first-week gross for a perfume. In October 2004, Spears took a career break to start a family. Greatest Hits: My Prerogative, her first greatest hits compilation album, was released in November 2004. Spears's cover version of Bobby Brown's "My Prerogative" was released as the lead single from the album, reaching the top of the charts in Finland, Ireland, Italy, and Norway. The second single, "Do Somethin'", was a top ten hit in Australia, the United Kingdom, and other countries of mainland Europe. In August 2005, Spears released "Someday (I Will Understand)", which was dedicated to her first son, who was born the following month. In November 2005, she released her first remix compilation, B in the Mix: The Remixes, which consists of 11 remixes.

In February 2006, pictures surfaced of Spears driving with her son on her lap instead of in a car seat. Child advocates were horrified by the photos of her holding the wheel with one hand and him with the other. Spears attributed the situation to a frightening encounter with paparazzi, and that it was a mistake on her part. The following month, she guest-starred on the Will & Grace episode "Buy, Buy Baby" as closeted lesbian Amber-Louise. She announced she no longer studied Kabbalah in May 2006, explaining, "my baby is my religion". Spears posed nude for the August 2006 cover of Harper's Bazaar; the photograph was compared to Demi Moore's 1991 Vanity Fair cover. In September 2006, her second son was born. Two months later, Spears filed for divorce from Federline, citing irreconcilable differences. Their divorce was finalized in July 2007, when the two reached a settlement and agreed to share joint custody of their sons.

Spears's maternal aunt, Sandra Bridges Covington, with whom she had been very close, died of ovarian cancer in January 2007. In February, Spears stayed in a drug rehabilitation facility in Antigua for less than a day. The following night, she shaved her head with electric clippers at a hair salon in Tarzana, Los Angeles. She admitted herself to other treatment facilities during the following weeks. In May 2007, she produced a series of promotional concerts at House of Blues venues, titled The M+M's Tour. In October 2007, Spears lost physical custody of her sons to Federline. The reasons for the court ruling were not revealed to the public. Spears was also sued by Louis Vuitton over her 2005 music video "Do Somethin'" for upholstering her Hummer interior in counterfeit Louis Vuitton cherry blossom fabric, which resulted in the video being banned on European TV stations.

In October 2007, Spears released her fifth studio album, Blackout. The album debuted atop the charts in Canada and Ireland, at number two in the US, France, Japan, Mexico, and the United Kingdom, and the top ten in Australia, South Korea, New Zealand, and many European nations. In the United States, it was Spears's first album not to debut at number one, although, she did become the only female artist to have her first five studio albums debut at the two top slots of the chart. The album received positive reviews from critics and had sold 3.1 million copies worldwide by the end of 2008. Blackout won Album of the Year at the 2008 MTV Europe Music Awards and was listed as the fifth Best Pop Album of the Decade by The Times.

Spears performed the lead single, "Gimme More", at the 2007 MTV Video Music Awards. The performance was widely panned by critics. Despite the criticism, the single enjoyed worldwide success, peaking at number one in Canada and within the top ten in almost every country it charted. The second single, "Piece of Me", reached the top of the charts in Ireland and reached the top five in Australia, Canada, Denmark, New Zealand, and the United Kingdom. The third single, "Break the Ice", was released the following year, and reached numbers seven and nine in Ireland and Canada, respectively. In December 2007, Spears began a relationship with paparazzo Adnan Ghalib.

In January 2008, after Spears refused to relinquish custody of her sons to Federline's representatives, she was institutionalized at Cedars-Sinai Medical Center due to her worsening mental condition. Her visitation rights were suspended at an emergency court hearing, and Federline was given sole custody. By the end of the month, she was put on a 5150 involuntary psychiatric hold at Ronald Reagan UCLA Medical Center. In February, her father Jamie filed a temporary conservatorship suit, granting him and attorney Andrew Wallet temporary control over her affairs. The following month, Spears guest-starred on the How I Met Your Mother episode "Ten Sessions" as a receptionist. Her performance drew positive reviews and brought the series its highest ratings ever. In July 2008, Spears regained some visitation rights after coming to an agreement with Federline.

In September 2008, Spears opened the MTV Video Music Awards with a pre-taped comedy sketch with Jonah Hill and an introduction speech. She won Best Female Video, Best Pop Video, and Video of the Year for "Piece of Me". A 60-minute introspective documentary, Britney: For the Record, was produced to chronicle Spears's return to the recording industry. Directed by Phil Griffin, For the Record was shot in Beverly Hills, Hollywood, and New York City during the third quarter of 2008. The documentary was broadcast on MTV to 5.6 million viewers for the two airings on the premiere night, December 1. It was the highest rating in its Sunday night time slot and in the network's history.

Spears's sixth studio album, Circus, was released in December 2008, two months after her conservatorship was extended indefinitely. It received positive reviews from critics and debuted at number one in Canada, the Czech Republic, and the United States, and within the top ten in many European nations. In the United States, Spears became the youngest female artist to have five albums debut at number one, earning a place in Guinness World Records. (Justin Bieber is the youngest male artist to do so, at age 18.) She also became the only act in the SoundScan era to have four albums debut with 500,000 or more copies sold. The album was one of the fastest-selling albums of the year and has sold 4 million copies worldwide. Its lead single, "Womanizer", became Spears's first chart-topper on the Billboard Hot 100 since "...Baby One More Time". The single also topped the charts in Belgium, Canada, Denmark, Finland, France, Norway, and Sweden. It was also nominated for the Grammy Award for Best Dance Recording.

In January 2009, Spears and Jamie obtained a restraining order against her former manager Sam Lutfi, ex-boyfriend Adnan Ghalib, and attorney Jon Eardley, who were accused of conspiring to gain control of Spears's affairs. Spears began the Circus Starring Britney Spears tour that March. With a gross of US $131.8 million, it became the fifth highest-grossing tour of the year. In November 2009, Spears released her second greatest hits album, The Singles Collection. The album's only single, "3", became her third number-one single in the US.

In May 2010, Spears's representatives confirmed she was dating her agent, Jason Trawick, and that they had decided to end their professional relationship to focus on their personal relationship. Spears designed a limited edition clothing line for Candie's, which was released in stores in July 2010. In September 2010, she made a cameo appearance on a Spears-themed tribute episode of the television series Glee, titled "Britney/Brittany". The episode drew the series's highest Nielsen rating so far in the 18–49 demographic.

In March 2011, Spears released her seventh studio album, Femme Fatale. The album peaked at number one in the United States, Canada, and Australia, and within the top ten on nearly every other chart. Its peak in the United States tied Spears with Mariah Carey and Janet Jackson for the third-most number ones among women. Femme Fatale has been certified platinum by the RIAA and, as of February 2014, had sold 2.4 million copies worldwide.

The album's lead single, "Hold It Against Me", debuted atop the Billboard Hot 100, becoming Spears's fourth number-one single on the chart and making her the second artist in history to have two consecutive singles debut at number one, after Mariah Carey. The second single, "Till the World Ends", peaked at number three on the Billboard Hot 100 in May, while the third single, "I Wanna Go", reached number seven in August. Femme Fatale became Spears's first album to have three of its songs reach the top ten on that chart. The fourth and final single, "Criminal", was released in September 2011. The music video sparked controversy when British politicians criticized Spears for using replica guns while filming the video in a London area that had been badly affected by the 2011 England riots. Spears's management briefly responded, stating, "The video is a fantasy story featuring Britney's boyfriend, Jason Trawick, which literally plays out the lyrics of a song written three years before the riots ever happened." In April 2011, Spears appeared in a remix of Rihanna's song "S&M". It reached number one in the US later that month, giving Spears her fifth number one on the chart. On Billboard's 2011 Year-End list, Spears was ranked number fourteen on the Artists of the Year, thirty-two on Billboard 200 artists, and ten on Billboard Hot 100 artists. Spears co-wrote "Whiplash", a song from the album When the Sun Goes Down (2011) by Selena Gomez & the Scene.

In June 2011, Spears embarked on her Femme Fatale Tour. The first ten dates of the tour grossed $6.2 million, and the tour peaked at number 55 on Pollstar's Top 100 North American Tours list for the halfway point of the year. The tour ended on December 10, 2011, in Puerto Rico, after 79 performances. A DVD of the tour was released in November 2011. In August 2011, Spears received the Michael Jackson Video Vanguard Award at the 2011 MTV Video Music Awards. The next month, she released her second remix album, B in the Mix: The Remixes Vol. 2. In December 2011, Spears became engaged to Trawick. Trawick was legally granted a role as co-conservator, alongside Jamie, in April 2012.

In May, Spears replaced Nicole Scherzinger as a judge for the second season of the American version of The X Factor, joining Simon Cowell, L.A. Reid, and fellow new judge Demi Lovato, who replaced Paula Abdul. With a reported salary of $15 million, she became the highest-paid judge on a singing competition series in television history. However, Katy Perry broke her record in 2018 after Perry was signed for a $25 million salary to serve as a judge on ABC's revival of American Idol. Spears mentored the Teens category; her final contestant, Carly Rose Sonenclar, was named the runner-up of the season. After Spears decided not to return, Paulina Rubio was hired as her permanent replacement for the show's third and final season.

That year, Spears collaborated with will.i.am on "Scream & Shout", released as the third single from his fourth studio album, #willpower (2013). The song later became Spears's sixth number-one single on the UK Singles Chart and peaked at number three on the Billboard Hot 100. "Scream & Shout" was among the best-selling songs of 2012 and 2013, with denoting sales of over 8.1 million worldwide. The accompanying music video was the third most-viewed in 2013 on Vevo, despite being released in 2012.[failed verification] In December 2012, Forbes named her music's top-earning woman of 2012, with estimated earnings of $58 million.

Spears began production on her eighth studio album, Britney Jean, in December 2012 and enlisted will.i.am as its executive producer in May 2013. In January 2013, Spears and Jason Trawick ended their engagement. Trawick was also removed as Spears's co-conservator, restoring her father as the sole conservator. Following the breakup, she began dating David Lucado in March; the couple split in August 2014. During the production of Britney Jean, Spears recorded the song "Ooh La La" for the soundtrack of The Smurfs 2, which was released in June 2013.

On September 17, 2013, she appeared on Good Morning America to announce her two-year concert residency at Planet Hollywood Resort & Casino in Las Vegas, titled Britney: Piece of Me. It began on December 27, 2013, and included a total of 100 shows throughout 2014 and 2015. During the same appearance, Spears announced that Britney Jean would be released on December 3, 2013, in the United States. It was released through RCA Records due to the disbandment of Jive Records in 2011, which had formed the joint RCA/Jive Label Group (initially known as BMG Label Group) between 2007 and 2011.

Britney Jean became Spears's final project under her original recording contract with Jive, which had guaranteed the release of eight studio albums. The record received a low amount of promotion and had little commercial impact, reportedly due to time conflicts involving preparations for Britney: Piece of Me. Upon its release, the record debuted at number four on the US Billboard 200 with first-week sales of 107,000 copies, becoming her lowest-peaking and lowest-selling album in the United States. It was also her lowest-charting and lowest-selling album in the UK, debuting at number 34 on the UK Albums Chart, selling 12,959 copies in its first week.

"Work Bitch" was released as the lead single from Britney Jean in September 2013. It debuted and peaked at number 12 on the US Billboard Hot 100, marking Spears's 31st entry on the chart, the fifth-highest debut of her career on the chart, and her seventh in the top 20. It also marked Spears's 19th top-20 entry and her 23rd top-40 single overall. It was her highest-sales debut since her 2011 number-one single "Hold It Against Me". "Work Bitch" debuted and peaked at number seven on the UK Singles Chart. The song also peaked within the top ten of the charts in Brazil, Canada, France, Italy, Mexico, and Spain.

The second single, "Perfume", premiered in November 2013. It debuted and peaked at number 76 on the US Billboard Hot 100. In October 2013, Spears was featured as a guest vocalist on the song "SMS (Bangerz)" by Miley Cyrus, from the latter's fourth studio album, Bangerz (2013). On January 8, 2014, Spears won Favorite Pop Artist at the 40th People's Choice Awards at the Microsoft Theater in Los Angeles. In August 2014, Spears confirmed she had renewed her contract with RCA and that she was writing and recording new music for her next album.

Spears announced via Twitter in August 2014 that she would be releasing an intimate apparel line called "The Intimate Britney Spears". It was available to be purchased beginning on September 9, 2014, in the United States and Canada through Spears's Intimate Collection website. It was available on September 25 for purchase in Europe. The company now ships to over 200 countries, including Australia and New Zealand. On September 25, 2014, Spears confirmed on Good Morning Britain that she extended her contract to perform her Britney: Piece of Me concert residency at Planet Hollywood Las Vegas for two additional years. Spears began dating television producer Charlie Ebersol in October 2014. The pair split in June 2015.

On May 14, 2015, Spears released a single, "Pretty Girls", with Iggy Azalea. It reached number 29 on the Billboard Hot 100. Spears and Azalea performed the track live at the 2015 Billboard Music Awards from The AXIS, the home of Spears's residency, to positive critical response. Entertainment Weekly praised the performance, noting "Spears gave one of her most energetic televised performances in years."

On June 16, 2015, Giorgio Moroder released the album Déjà Vu, which featured Spears on "Tom's Diner". The song was released as the fourth single from the album on October 9, 2015. In an interview, Moroder praised Spears's vocals and said she "sounds so good that you would hardly recognize her". At the 2015 Teen Choice Awards, Spears received the Candie's Style Icon Award, her ninth Teen Choice Award. In November 2015, Spears guest-starred as a fictionalized version of herself on the CW series Jane the Virgin. On the show, she danced to "Toxic" with Gina Rodriguez's character.

In November 2015, Spears confirmed via social media that she had begun recording her ninth studio album. On March 1, 2016, V announced that Spears would appear on the cover of its 100th issue, dated March 8, 2016, in addition to revealing three different covers shot by photographer Mario Testino for the milestone publication. The V editor-in-chief, Stephen Gan, said Spears was selected because of her status as an icon in the industry, and asked: "Who in our world did not grow up listening to her music?" In May 2016, Spears launched a casual role-play gaming application, Britney Spears: American Dream. The app, created by Glu Mobile, was made available through both iOS and Google Play.

On May 22, 2016, Spears performed a medley of her past singles at the 2016 Billboard Music Awards. In addition to opening the show, Spears was honored with the Billboard Millennium Award. On July 15, 2016, Spears released the lead single, "Make Me", from her forthcoming album, featuring guest vocals from American rapper G-Eazy. The album, Glory, was formally released on August 26, 2016. On August 16, 2016, MTV and Spears announced that she would perform at the 2016 MTV Video Music Awards. The performance marked Spears's first time returning to the VMA stage after her widely panned performance of "Gimme More" at the 2007 show nine years earlier. Along with "Make Me", Spears and G-Eazy also performed the latter's hit song "Me, Myself & I".

Spears appeared on the cover of Marie Claire UK for the October 2016 issue. In the publication, Spears revealed that she had suffered from crippling anxiety in the past, and that motherhood played a major role in helping her overcome it. "My boys don't care if everything isn't perfect. They don't judge me", Spears said in the issue. In November 2016, during an interview with Las Vegas Blog, Spears confirmed she had already begun work on her next album, stating: "I'm not sure what I want the next album to sound like... I just know that I'm excited to get into the studio again and actually have already been back recording." In the same month, she released a remix version of "Slumber Party" as the second single from Glory, featuring Tinashe.

She began dating "Slumber Party"'s music video co-star Sam Asghari after the two met on set. In January 2017, Spears received four wins out of four nominations at the 43rd People's Choice Awards, including Favorite Pop Artist, Female Artist, Social Media Celebrity, as well as Comedic Collaboration for a skit with Ellen DeGeneres for The Ellen DeGeneres Show. In March 2017, Spears announced that her residency concert would be performed abroad as a world tour, Britney: Live in Concert, with dates in select Asian cities. In April 2017, the Israeli Labor Party announced that it would reschedule its July primary election to avoid conflict with Spears's sold-out Tel Aviv concert, citing traffic and security concerns.

Spears's manager Larry Rudolph also announced the residency would not be extended following her contract expiration with Caesars Entertainment at the end of 2017. On April 29, 2017, Spears became the first recipient of the Icon Award at the 2017 Radio Disney Music Awards. On November 4, 2017, Spears attended the grand opening of the Nevada Childhood Cancer Foundation Britney Spears Campus in Las Vegas. Later that month, Forbes announced that Spears was the eighth-highest-earning female musician, earning $34 million in 2017. On December 31, 2017, Spears performed the final show of Britney: Piece of Me. The final performance reportedly brought in $1.172 million, setting a new box office record for a single show in Las Vegas, a record previously held by Jennifer Lopez. Performances of "Toxic" and "Work Bitch" were recorded on earlier dates and aired on ABC's Dick Clark's New Year's Rockin' Eve to a record audience of 25.6 million.

In January 2018, Spears released her 24th perfume with Elizabeth Arden, Sunset Fantasy, and announced the Piece of Me Tour, which took place in July 2018 in North America and Europe. Tickets were sold out within minutes for major cities, and additional dates were added to meet the demand. Pitbull was the supporting act for the European leg. The tour ranked at 86 in North America and 30 worldwide on Pollstar's 2018 Year-End Top 100 Tours chart. In total, the tour grossed $54.3 million, with 260,531 tickets sold, and was the sixth-highest-grossing female tour of 2018. It was also the United Kingdom's second-best-selling female tour of 2018.

On March 20, 2018, Spears was announced as part of a campaign for French luxury fashion house Kenzo. The company said it aimed to shake up the "jungle" world of fashion with Spears's "La Collection Memento No. 2" campaign. On April 12, 2018, Spears was honored with the 2018 GLAAD Vanguard Award at the GLAAD Media Awards for her role in "accelerating acceptance for the LGBTQ community". On April 27, 2018, Epic Rights announced a new partnership with Spears to debut her own fashion line in 2019, which would include clothing, fitness apparel, accessories, and electronics.

In July 2018, Spears released her first unisex fragrance, Prerogative. On October 18, 2018, Spears announced her second Las Vegas residency show, Britney: Domination, which was set to launch at Park MGM's Park Theatre on February 13, 2019. Spears was slated to make $507,000 per show, which would have made her the highest paid act on the Las Vegas Strip. On October 21, 2018, Spears performed at the Formula One Grand Prix in Austin, the final performance of her Piece of Me Tour.

By early 2019, Spears announced an indefinite hiatus and the cancellation of her Las Vegas residency after her father, Jamie, suffered a near-fatal colon rupture and Andrew Wallet resigned as co-conservator of her estate. Following allegations of Jamie's involvement in cancelling Spears's residency and placing her in a psychiatric facility, a movement titled #FreeBritney was organized in May 2019. Judge Brenda Penny announced a professional evaluation of the conservatorship that month. That September, Kevin Federline filed a restraining order against Jamie following an alleged physical altercation between Jamie and one of her sons.

An interactive pop-up museum dedicated to Spears, dubbed "The Zone", opened in Los Angeles in February 2020, though it was later suspended due to the COVID-19 pandemic. She released Glory's Japanese-exclusive bonus track, "Mood Ring" as a single, and debuted a new cover of the album to streaming and digital platforms worldwide in May 2020. In December, Spears released an updated deluxe edition of Glory, which includes "Mood Ring" and new songs "Swimming in the Stars" and "Matches", a collaboration with Backstreet Boys.

In February 2021, a television documentary titled Framing Britney Spears aired on FX. That June, The New York Times obtained confidential court documents stating that Spears had pushed for years to end her conservatorship. At the conservatorship hearing, Spears announced her intentions to terminate the conservatorship, citing abuse. In July, Bessemer Trust and Spears's longtime manager Larry Rudolph resigned. Later in the year, Spears announced her engagement to her longtime boyfriend, Sam Asghari. After Jamie filed a suit to end his involvement, Penny terminated Spears's conservatorship in November.

In April 2022, she announced her pregnancy with Asghari's child, which ended in a miscarriage the following month. The couple married on June 9 at her home in Thousand Oaks, Los Angeles. None of Spears's immediate family (including her parents, sister, and brother) were invited; her two sons did not attend. Spears's ex-husband, Jason Alexander, attempted to crash the wedding by breaking into her home, armed with a knife, but was arrested. A three-year restraining order was subsequently enacted. On August 26, Spears and English musician Elton John released the duet "Hold Me Closer", a remake of John's 1972 single "Tiny Dancer". It was Spears's first musical release since dissolving her conservatorship. "Hold Me Closer" debuted at number six on the US Billboard Hot 100, becoming her 14th top-ten single and her highest-charting song in the chart since "Scream & Shout" (2012). It debuted at number three on the UK Singles Chart, earning Spears her 24th top-ten.

Since her conservatorship's dissolution, Spears's personal life, social media presence, and overall well-being have been subject to renewed media interest and fan speculation, giving rise to conspiracy theories. On January 24, 2023, deputies from the Ventura County Sheriff's Office performed a welfare check at Spears's residence after receiving several calls from fans who were concerned after she deleted her Instagram account. A spokesperson for the Sheriff's Department stated that Spears "was safe and in no danger". Spears addressed the incident on her Twitter account, asking fans to respect her privacy. Spears and the rapper will.i.am released their single, "Mind Your Business", on July 21, 2023. On August 16, it was announced Spears and Asghari separated after 14 months of marriage. On May 1, 2024, they reached a divorce settlement. The following day, the judge signed off on the settlement and the couple were divorced on December 2, 2024. In September 2023, an additional welfare check was initiated when Spears posted an Instagram video of herself dancing with knives. Her security team assured the attending officer that there was no immediate threat to her safety, and the officer departed. Spears also clarified that the knives were not real.

After signing a $15 million book deal in February 2022 in one of the largest deals ever made, she published a second memoir, The Woman in Me, in October 2023. It details her rise to fame, public media events, her conservatorship, and her newfound freedom. In the United States, it sold 1.1 million copies, while worldwide it sold 2.4 million copies in print sales during its first week of release.

In January 2024, reports circulated that Charli XCX and Julia Michaels had been asked to write songs for Spears, and Rolling Stone reported that "management and A&R are trying to get her excited for the music". Spears denied the reports, saying she would never return to the music industry. However, she also said that she had written more than 20 songs for other artists in the previous two years. In May 2024, Charli XCX confirmed in an interview that she had indeed been asked to write for Spears, for which she traveled to Malibu, but that she did not know if Spears was involved, explaining that "the team were present... But she didn't record it. She obviously didn't."

In 2026, she clarified her exit from the music industry, saying that she would "never perform in the US again", but did not rule out performing elsewhere, saying "I hope to be ... performing with my son … in the UK and Australia very soon."

In February 2026, Variety reported that music publisher Primary Wave had acquired the rights to Spears' entire music catalog along with other rights. The BBC reported that the purchase took place on December 30, 2025, for roughly $200 million. The following month, she was arrested in Ventura County, California, on suspicion of driving under the influence. In April, Spears' representative stated that she had checked herself into a rehabilitation facility. On April 30, 2026, she would be officially given a criminal DUI charge. Spears was scheduled to appear in court for her arraignment hearing May 4, 2026. It had been agreed that Spears could avoid jail time for this charge if she pled guilty to reckless driving, for which she would only get probation and be required to both complete a DUI class and pay state-mandated fines and fees.

On April 30, 2026, Spears checked out of rehab. On May 4, 2026, Spears, who was absent from court during her arraignment hearing and had her defense attorney appear on her behalf, pled guilty in a Ventura County court to one count of reckless driving. She was then sentenced to one year of probation and one day in jail, with credit for the time in jail she served following her March 2026 arrest. In addition, Spears was ordered to meet with a psychologist once a week and a psychiatrist twice a month. She was also fined $571 and is required to attend a three-month DUI program which sees drivers complete 30 hours of class time. As part of her plea deal, Spears' vehicle became authorized to be searched for drugs and alcohol.

Spears has cited Madonna, Janet Jackson, and Whitney Houston as major influences, her "three favorite artists" as a child, whom she would "sing along to ... day and night in [her] living room"; Houston's "I Have Nothing" was the song she auditioned to that landed her record deal with Jive Records. Spears also named Mariah Carey as "one of the main reasons I started singing". Throughout her career, Spears has drawn frequent comparisons to Madonna and Jackson in particular, in terms of vocals, choreography, and stage presence. According to Spears: "I know when I was younger, I looked up to people ... like, you know, Janet Jackson and Madonna. And they were major inspirations for me. But I also had my own identity and I knew who I was."

In the 2002 book Madonnastyle by Carol Clerk, Spears is quoted saying: "I have been a huge fan of Madonna since I was a little girl. She's the person that I've really looked up to. I would really, really like to be a legend like Madonna." Spears cited "That's the Way Love Goes" as the inspiration for her song "Touch of My Hand" from her album In the Zone, saying "I like to compare it to 'That's the Way Love Goes,' kind of a Janet Jackson thing." She also said her song "Just Luv Me" from her Glory album also reminded her of "That's the Way Love Goes".

After personally meeting Spears, Jackson stated: "she said to me, 'I'm such a big fan; I really admire you.' That's so flattering. Everyone gets inspiration from some place. And it's awesome to see someone else coming up who's dancing and singing, and seeing how all these kids relate to her. A lot of people put it down, but what she does is a positive thing." Madonna said of Spears in the documentary Britney: For the Record: "I admire her talent as an artist ... There are aspects about her that I recognize in myself when I first started out in my career." Spears has also named Michael Jackson, Mariah Carey, Sheryl Crow, Otis Redding, Shania Twain, Brandy, Beyoncé, Natalie Imbruglia, Cher, and Prince as inspirations, and younger artists such as Selena Gomez and Ariana Grande.

Spears is described as a pop artist and generally explores the genre in the form of dance-pop. Following her debut, she was credited with influencing the revival of teen pop in the late 1990s. Rob Sheffield of Rolling Stone wrote: "Spears carries on the classic archetype of the rock & roll teen queen, the dungaree doll, the angel baby who just has to make a scene." In a review of ...Baby One More Time, Stephen Thomas Erlewine of AllMusic described her music as a "blend of infectious, rap-inflected dance-pop and smooth balladry". Oops!... I Did It Again saw Spears working with several R&B producers to create "a combination of bubblegum, urban soul, and raga". Her third studio album, Britney, derived from the teen pop niche "[r]hythmically and melodically", but was described as "sharper, tougher than what came before", incorporating genres such as R&B, disco, and funk.

Spears has explored and heavily incorporated the genres of electropop and dance music in her records, as well as influences of urban and hip-hop, which are most present on In the Zone and Blackout. In the Zone also experiments with Euro trance, reggae, and Middle Eastern music. Femme Fatale and Britney Jean were also heavily influenced by electronic music genres. Spears's ninth studio album, Glory, is more eclectic and experimental than her previously released work. She commented that it "took a lot of time ... it's really different ... there are like two or three songs that go in the direction of more urban that I've wanted to do for a long time now, and I just haven't really done that."

...Baby One More Time and Oops!... I Did It Again address themes such as love and relationships from a teenager's point of view. Following the massive commercial success of her first two studio albums, Spears's team and producers wanted to maintain the formula that took her to the top of the charts. Spears, however, was no longer satisfied with the sound and themes covered on her records. She co-wrote five songs and choose each track's producer on her third studio album, Britney, whose lyrics address the subjects of reaching adulthood, sexuality, and self-discovery. Sex, dancing, freedom, and love continued to be Spears's main subjects on her subsequent albums. Her fifth studio effort, Blackout, also addresses issues such as fame and media scrutiny, including on the song "Piece of Me".

Spears's music has also been noted for some catchphrases. The opening in her debut single "...Baby One More Time", "Oh, baby baby" is considered to be one of her signature lines and has been parodied in the media by various artists such as Nicole Scherzinger and Ariana Grande. It has been used in various forms throughout her music, such as simply, "baby" and "oh baby", as well as the Blackout track, "Ooh Ooh Baby". On the initial development of "...Baby One More Time", Barry Weiss noted Spears's inception of the catchphrase from her strange ad-libbing during the recording of the song. He commented further, "We thought it was really weird at first. It was strange. It was not the way Max wrote it. But it worked! We thought it could be a really good opening salvo for her." The opening line in "Gimme More", "It's Britney, bitch" has become another signature phrase. An early review of Blackout suggested the phrase was "simply laughable". Amy Roberts of Bustle called it "an indelible cultural turning point, transforming a frenetic, floundering moment in the superstar's career to one of strength and empowerment".

Referred to as the "Princess of Pop", Spears was credited as one of the "driving force[s] behind the return of teen pop in the late 1990s". Rolling Stone's Stacy Lambe explained that she "help[ed] to usher in a new era for the genre that had gone dormant in the decade that followed New Kids on the Block. ... Spears would lead an army of pop stars ... built on slick Max Martin productions, plenty of sexual innuendo and dance-heavy performances. [She became] one of the most successful artists of all time—and a cautionary tale for a generation, whether they paid attention or not." In a 2021 article for Time, Maura Johnston opined that "Spears's legacy as a pop artist is complex, made up of dazzling musical heights and music-business-borne lows". Johnston also commented: "While Spears's catalog is part of the canon that defines the first 20 years of this millennium, one hopes that her public struggles, and the strength she's shown while enduring them, will lead to her cementing her true legacy: Reshaping the machine that turns those songs into cultural touchstones."

Glamour contributor Christopher Rosa described her as "one of pop music's defining voices. ... When she emerged onto the scene in 1998 with ...Baby One More Time, the world hadn't seen a performer like her. Not since Madonna had a female artist affected the genre so profoundly." Billboard's Robert Kelly observed that Spears's "sexy and coy" vocals on her debut single "...Baby One More Time" "kicked off a new era of pop vocal stylings that would influence countless artists to come". In 2020, Rolling Stone ranked the song at number one on a list of the 100 Greatest Debut Singles of All Time and Rob Sheffield described it as "One of those pop manifestos that announces a new sound, a new era, a new century. But most of all, a new star ... With "...Baby One More Time", [Spears] changed the sound of pop forever: It's Britney, bitch. Nothing was ever the same."

Spears was at the forefront of the female teen pop explosion starting in 1999 and extending through the 2000s, leading the pack of Christina Aguilera, Jessica Simpson, and Mandy Moore. All of these performers had been developing material in 1998, but the market changed dramatically in December 1998 when Spears's single and video were charting highly. RCA Records quickly signed Aguilera and released her debut single to capitalize on Spears's success, producing her debut hit single "Genie in a Bottle". Simpson consciously modeled her persona as more mature than Spears; her "I Wanna Love You Forever" charted in September 1999, and her album Sweet Kisses followed shortly after. Moore's first single, "Candy", hit the airwaves a month before Simpson's single. Fueling media stories about their competition for first place, Spears and Aguilera traded barbs but also compliments through the 2000s.

Alim Kheraj of Dazed called Spears "one of pop's most important pioneers". After eighteen years as a performer, Billboard described her as having "earned her title as one of pop's reigning queens. Since her early days as a Mouseketeer, [Spears] has pushed the boundaries of 21st century sounds, paving the way for a generation of artists to shamelessly embrace glossy pop and redefine how one can accrue consistent success in the music industry." Entertainment Weekly's Adam Markovitz described Spears as "an American institution, as deeply sacred and messed up as pro wrestling or the filibuster." She was ranked at number six on Billboard's 2024 Greatest Pop Stars of the 21st Century list and number 14 on its 2025 "Top 100 Women Artists of the 21st Century" list.

Spears has been credited with redefining Las Vegas residencies as a retirement place for musicians. Her debut concert residency Britney: Piece of Me was described as "the natural evolution of Celine Dion's powerhourse Vegas residency, a still-charting star of another generation redefining the role of Strip headliner." Forbes named Spears the sixth-highest-earning female musician of 2015. She is credited with influencing and paving the way for other artists's residencies such as Jennifer Lopez's Jennifer Lopez: All I Have, Bruno Mars's Bruno Mars at Park MGM, and Backstreet Boys' Backstreet Boys: Larger Than Life. The arrival of Spears "saw the pop promoters finally tap into the younger crowd arriving in town for a good time".

Spears's much-publicized personal problems and her subsequent career comeback have inspired some artists. Gwyneth Paltrow's character in the 2010 film Country Strong was inspired by Spears's treatment by the media. According to film director Shana Fest, "that's where this movie came from. I mean, I was seeing what was happening in the media to Britney Spears. I think it's tragic how we treat people who give us so much, and we love to see them knocked down to build them back up again, to knock them down again." Nicki Minaj has cited Spears's comeback after her much-publicized personal issues as an inspiration. Spears's hounding by paparazzi and personal problems also inspired Barry Manilow's album 15 Minutes. Manilow said: "She couldn't have a life without them pulling up next to her car and following her and driving her crazy to the point where, that was around the time she shaved off her hair. ... We all looked at it in horror ... So it seemed like a thing to be writing an album about." Bebo Norman wrote a song about Spears, called "Britney", which was inspired by "culture's make-or-break treatment of celebrities". Along with Alicia Silverstone, Christy Turlington, and Naomi Campbell, Spears has been credited with introducing the navel piercing to mainstream culture.