"Happy" is a song performed by British singer Leona Lewis for her second studio album Echo (2009).

It received generally positive reviews from music critics, praising the production and, some of them, calling it a "number one song".

My goal when I started working on Leona's new album was to '[not]' chase or be influenced by any of her previous hits—or any songs [I]'ve ever done with anyone else—including 'Bleeding Love'.

True artists do not look back to previous successes; they look forward to creating new moments and songs the world can connect with in a different way.

[6] "Happy" is a pop and R&B ballad,[1] song written in C major; Lewis' vocal range extends from G3 to C6.

It has been described as "an amazing song" by Rick Krim, the executive producer of VH1 Divas,[10] while a reviewer for music website Popjustice said, "In short: the Leona Lewis single is above average.

[...] It's a really strong lead single that sounds like a number one, and a typically muscular production from Tedder, but above all it's a powerful and moving song".

[13] Entertainment Weekly critic Michael Slezak wrote that "while "Happy" is a solidly written, professionally produced song with a Velcro-ey hook, it has the emotional resonance of a so-so, big-budget romantic comedy.

[...] In the hands of a singer who could achieve both technical perfection and emotional depth, 'Happy' might've been my early autumn jam.

But delivered in Lewis's lovely-but-vacant style, I'm gonna have to rifle through my iPod for a more substantial diva anthem".

[24] The song made its first European chart appearance when it debuted at 25 in Sweden on 2 October 2009, peaking at number 11 the following week.

[10][31] On 26 October, Lewis was a guest on the BBC's The One Show where she talked about "Happy", Echo and her pictorial autobiography, Dreams.

[37] The Jason Nevins remix of the song was used as runway-soundtrack for the 2009 Victoria's Secret Fashion Show airing on 1 December 2009.