Three of the band's members spoke to ITV London's Lucrezia Millarini on the red carpet.
Even with its long history of hosting film premieres, London's West End has never seen anything quite like this. Tens of thousands of fans have been cramming themselves into every corner of Leicester Square since first thing this morning, to get a glimpse of One Direction.
Sangeeta Kandola went to meet their dedicated army of fans.
Niall, Louis and Liam from One Direction have spoken to ITV News ahead of the world premiere of 'One Direction: This is Us' at Leicester Square in London.
Harry Styles is "excited" about One Direction's This Is Us film premiere, the boyband's Twitter page states.
Fans of One Direction are anxiously waiting in Leicester Square ahead of the world premiere of the band's film, This Is Us.
One Direction's Niall Horan said he is "just pinching myself" ahead of today's This Is Us film premiere:
Holy crap! today is the day! We are actually doing a movie premiere ! Can't wait !
Just pinching myself! Absolutely huge day today! We want u to know that u made this all happen! And when u see the film or are standing on
Leicester square tonight! U can all turn to eachother and be like "we did this" so thank you so much
One Direction's first movie premieres today ... but what does it have in store for the boyband's fans?Read the full story ›