Born and raised in the Islington section of north London, Lewis won a talent show at the age of 13 and devoted herself to music thereafter, eventually graduating from the prestigious BRIT School for Performing Arts and Technology. While working as a receptionist and pizza waitress and writing her own material, Lewis auditioned for The X Factor in the summer of 2006 and won the third series' competition in December of that year. Lewis' debut single, a soulful cover of Kelly Clarkson's "A Moment Like This" (Clarkson's own debut American Idol showcase single), was the number one single in the U.K. at the turn of the year, including the coveted "Christmas number one."

Along with her TV-driven U.K. success, Lewis signed an American recording deal with Clive Davis' J Records in February 2007. By the end of the year, she had launched her debut album, Spirit, in England, and watched it go to the top of the charts (along with the single "Bleeding Love"). The American release followed in 2008 with similar success; it reached the top of the Billboard 200 and received a Grammy nomination for Best Pop Album. Echo, Lewis' follow-up, was issued in 2009, featuring collaborations with Ryan Tedder, Xenomania, and Timbaland. Also in 2009, Lewis released the single "I See You (Theme from Avatar)." Written by James Horner and Simon Franglen, the song was featured on the soundtrack to the hit James Cameron film Avatar. The following year, Lewis promoted Echo with the Labyrinth tour. Inspired by the 1986 fantasy film of the same name, the tour was showcased on the DVD/CD The Labyrinth Tour: Live from the O2 in 2010. In 2011, Lewis began recording her third studio album, Glassheart, showcasing writing and production by a bevy of names including Ryan Tedder, Fraser T. Smith, Dallas Austin, and others. The album had a long gestation period, during which it slowly became more electronic dance-oriented. It finally appeared in Europe in October 2012.

Glassheart didn't perform well on the charts -- it only went silver in the U.K. and never appeared in the U.S. -- and she split with her management, Modest!, in February 2013. At the end of the year, she released Christmas, With Love, a seasonal record in the style of A Christmas Gift for You from Phil Spector. In 2014, it was announced that she was parting ways with Sony Records and signing with Universal's Island subsidiary. On September 11, 2015 she released her first album for the label, I Am, which debuted at 12 in the U.K. but generated no major hits; its first single, "Fire Under My Feet," peaked at 51. In the summer of 2016, Lewis starred as Grizabella in a Broadway revival of Andrew Lloyd Webber's Cats, during which time she announced her split from Island and released the charity single "(We All Are) Looking for Home." ~ Stewart Mason