Annual UK festival kicks off with superstar lineup.
The 2015 Summertime Ball was held earlier today and every act brought their A game.
From Ariana Grande to Avicii, the pop festival, which is in its sixth year now, was fuelled by some serious star power.
Check out some of the best performances of the day:
Kelly Clarkson belts out Since U Been Gone:
Jason Derulo talked dirty to the massive crowd:
One Direction showed off some amazing vocals during Story Of My Life:
Ariana Grande had no Problem getting the crowd fired up:
Carly Rae Jepsen really really really really likes performing:
Ne-Yo put together a smooth as hell medley of his biggest hits:
Fifth Harmony's performance was Worth It:
Rita Ora's slightly awkward set was saved by her endless energy and super talented dancers:
Pitbull has no trouble getting throngs of beautiful women to share a stage with him - except for the only one anyone's checking for when it comes to Timber:
And finally, Little Mix brought the house down with a huge performance of Wings: