Pharrell Williams is asking fans to get happy by singing and dancing their way through a new United Nations initiative.

The superstar, who scored a huge hit with his track Happy in November (13), has teamed up with the Un Foundation to celebrate the global 'International Day of Happiness' on 20 March (14).

Williams wants his devotees to join in by uploading to videos of themselves having fun.

Organisers behind the initiative hope the campaign will pull in donations to aid Un humanitarian efforts.