It's Not Me, It's You is the second studio album by English singer Lily Allen, released on 4 February 2009 by Regal Recordings and Parlophone. It was produced and co-written by Greg Kurstin, with whom Allen had previously worked on her debut studio album, Alright, Still (2006). The album represents a departure from the ska and reggae influences of its predecessor, incorporating electropop with elements of jazz.

Upon release, It's Not Me, It's You received positive reviews from critics, praising Allen's "sharp tongue" and calling the album "wonderful". The album was a commercial success, debuting at number one on the charts in the United Kingdom, Australia and Canada. It was later certified triple platinum by the British Phonographic Industry (BPI) and has sold 1,070,340 copies in the UK alone. It was also certified four times platinum by the Australian Recording Industry Association (ARIA) for shipments of over 280,000 copies in Australia. The album has sold over two million copies worldwide.

The album's lead single, "The Fear", also debuted atop the UK Singles Chart, where it remained for four consecutive weeks. Other singles include the UK top-five entry "Not Fair", "Fuck You", "22" and "Who'd Have Known". The track "Back to the Start" was released as a limited-edition seven-inch vinyl for Record Store Day. Allen performed on a variety of television programs to promote the album, including Jimmy Kimmel Live! and The Ellen DeGeneres Show. She also embarked on her second concert tour, the It's Not Me, It's You World Tour, which visited Europe, North America, Asia, Oceania and South America.