Spears's success had made her notable in the music industry as well as popular culture. In early 2001 she caught the attention of Pepsi who gave Spears a multi-million dollar promotional deal which included numerous television commercials, point-of-purchase promotions and Internet ties between Spears and the company.[23]

Spears released her third studio album in November 2001. Britney was the first album on which Spears assumed some creative control co-writing five of the album's tracks. It had a successful debut at number one in the U.S. selling 745,744 units during its first week, and making her the only female artist in SoundScan history to have her first three albums debut at number one.[24][25] The album fared well with critics such as All Music Guide who gave it 4.5 out of 5 stars describing the album's title tracks as being "pivotal moments on Britney Spears' third album, the record where she strives to deepen her persona, making it more adult while still recognizably Britney."[26] In contrast Rolling Stone said of the album "Britney belabors the obvious: Spears is one month away from entering her twenties and clearly needs to grow up if she's going to bring her fans along."[27] The singles didn't perform as well; Britney's lead single I'm a Slave 4 U was able to peak at 27 on the Billboard Hot 100 making it the album's biggest hit.[28] To help promote the album, Spears embarked on the Dream Within a Dream Tour in November of 2001. The tour hit a sour note in Mexico City when she was forced to cut her last show short due to bad weather and upsetting her audience.[29]
Audio samples:

With the end of the tour, Spears announced she would take a 6 month break from her career.[30] Earlier that year Spears's four-year relationship with Justin Timberlake ended.[31] Speculation that Spears had been unfaithful began circulating due to Timberlake's 2002 song "Cry Me a River" and its subsequent music video.[32] The song's music video showed an actress playing what could be construed as a Britney look-alike with certain physical features resembling Spears. Timberlake has denied that it was meant to portray Britney.[33] Britney's break seemed to have ended when she returned to the spotlight in August 2003. In a performance at the MTV Video Music Awards, Spears appeared with Christina Aguilera performing the song "Like a Virgin" and both girls were later joined by Madonna. Spears and Aguilera each locked lips with Madonna in a highly-publicized kiss.[34][35][36]

In a September 2003 interview with Tucker Carlson of CNN, on the subject of the 2003 Iraq War, Spears said, "Honestly, I think we should just trust our president in every decision he makes and should just support that, you know, and be faithful in what happens."[37] The footage of this quote later appeared in Michael Moore's documentary Fahrenheit 9/11.
Spears performing in September 2003.
Spears performing in September 2003.

November 2003 saw the release of Spears's fourth studio album, In the Zone. Jettisoning the Max Martin-produced synthpop of her earlier releases, the album took in lesser-known producers such as RedZone and big names including Moby and R. Kelly. Spears co-wrote eight of the album's thirteen songs and co-produced some of her material for the first time. In the Zone went to the top of the U.S. charts in its debut week, selling over 609,000 copies. This made Spears the only female in music history to have her first four studio albums debut at number one.[38] The album had a mild reception from critics. Stylus Magazine gave the album a D and even blamed her career choices saying, "Ultimately, In the Zone suffers greatly from Britney's uneasy transition from teen tart to sexually powerful woman. Had Britney been in charge of her career direction instead of mercilessly prostituted by her management, she might have been able to produce something with some semblance of musical vision."[39] The Guardian praised the albums melodies and her effort giving it 4 out of 5 stars and writing, "Unlike previous Britney albums, In the Zone has no filler and no shoddy cover versions, just 57 varieties of blue-chip hit-factory pop. There is southern hip-hop, deep house, Neptunes-style R&B, the ubiquitous Diwali beat and, most importantly, oodles of Madonna."[40] The album spawned the international number one and U.S. top ten hit single, "Toxic", which won Spears her first Grammy in the category of Best Dance Recording.[1]