Lily Rose Beatrice Allen was born in May 1985 in Hammersmith, west London, to comedian Keith Allen and film producer Alison Owen. Allen has said that at age 11 she was singing an Oasis tune in the schoolyard when a teacher overheard her and told her she had talent and suggested she do something with it – she subsequently took singing lessons with the teacher, and in her free time listened to artists such as The Specials, T.Rex, and Happy Mondays. Allen made an appearance as a lady-in-waiting in the 1998 film “Elizabeth” (co-produced by her mother) but dropped out of school at 15. After a family holiday in Ibiza, Allen remained on the Spanish island, earning money by working at a Plastic Fantastic record store and dealing in ecstasy. Here she met her first manager, George Lamb, after he saved her from several assailants and sent her home, where, after being rejected by several labels, she used her father's connections to get signed to Warner Music in 2002. When the executive who had signed her left, the label lost interest and she left without releasing the folk songs they had presented her. Allen then studied horticulture with the intent of becoming a florist, but changed her mind and returned to music. She began writing songs, and in 2004 her manager introduced her to production duo Future Cut. The following year, Allen was signed to Regal Records, who gave her some finance to produce an album, but were unable to provide much further support for it due to their preoccupation with other releases (such as Coldplay's “X&Y” and Gorillaz' “Demon Days”). Allen created an account on MySpace and began posting demos in November 2005, attracting thousands of listeners, and 500 limited edition 7" vinyl singles of "LDN" were rush-released, reselling for as much as £40. Allen also produced 2 mixtapes, “My First Mixtape” and “My Second Mixtape”, to promote her work - they included tracks by Creedence Clearwater Revival, Dizzee Rascal, and Ludacris. Buoyed by the success her Myspace account was generating, Allen decided to work with producers Greg Kurstin and Mark Ronson, finishing the rest of her debut album in 2 weeks. “Alright, Still” was released in July 2006, initially as a limited edition 12" vinyl, and then as a full CD., and included the single “Smile” (a UK Singles chart number 1), “Alfie” (number 15 in the same chart) and "Littlest Things" (which, among other works, earned producer Mark Ronson a 2008 Grammy in the "Producer of the Year - Non Classical" category). In the US, “Alright, Still” was released in January 2007, selling 34,000 copies to occupy number 20 on the Billboard Album chart. “Alright, Still” was nominated for “Best British Album” at the 2007 BRIT Awards, and "Best Alternative Music Album" at the 2008 Grammy Awards. “Alright, Still” has sold over 2.5 million copies worldwide.

Second album, “It's Not Me, It's You”, was recorded mainly in L.A., with Greg Kurstin again looking after production.

Away from her solo career, Allen has provided backing vocals on the Basement Jaxx song "Lights Go Down" (from “Crazy Itch Radio”), appears on Robbie Williams's album, “Rudebox” (on the Manu Chao cover "Bongo Bong and Je Ne T'Aime Plus", produced by Mark Ronson), and provides vocals on "Rawhide" by Jamie T and "Wanna Be" by Dizzee Rascal. She sang on the Mark Ronson produced Kaiser Chiefs’ song "Oh My God", and has contributed the song "She's So Lovely and Naive" for the soundtrack of the 2008 British comedy film “Angus, Thongs and Perfect Snogging”.
She has been cast as Lydia Bennett in a spoof film version of Jane Austen's “Pride and Prejudice”, and in 2007 she signed a one series contract to present her own BBC Three TV show entitled “Lily Allen and Friends”. Guests on the first show were Cuba Gooding Junior and David Mitchell, and later guests included Mark Ronson, Joanna Page, James Corden, Lauren Laverne, Roisin Murphy, Louis Walsh and Danny Dyer. BBC Three has since announced it was renewing “Lily Allen and Friends” for a second season.