Mumford and Sons will headline Radio 1´s Big Weekend at Exeter's Powderham Castle.
They will be joined by international acts including The Weeknd, Iggy Azalea and Nick Jonas, plus the UK's Jess Glynne at Europe's biggest free ticketed event, which runs on May 28 and 29.
Folk-rock band Mumford and Sons will play Saturday's main stage for the first time, and lead singer Marcus Mumford joked the band had "five years' worth of riders" to make up for.
He said: "I've never been to Radio 1´s Big Weekend so we've got a lot of catching up to do. We're really excited, thanks for inviting us, it's going to be great."
They will appear alongside acts including Chase & Status, Stormzy, Craig David and Meghan Trainor on the Saturday.
Iggy will play on the Sunday alongside previously announced headliners Coldplay and artists including Ellie Goulding, OneRepublic and Catfish and the Bottlemen.
The Fancy singer said: "I've been waiting for you guys to announce it so that I could tell everybody because everyone keeps asking me when I'm coming to visit - and I knew that I was coming over for this but I couldn't tell anyone, and I'm very bad at keeping secrets, so I'm glad this is one less secret to keep.
"This will be the first time that I'm going to come back for a while."
The festival will host more than 50 acts across three stages: the Main Stage, the In New Music We Trust Stage and the BBC Introducing Stage.
Fifty thousand tickets were made available for the Big Weekend and were snapped up within an hour of going live earlier this month.
Tickets will now be available through Radio 1 giveaways, while performances will be streamed online and made available on iPlayer.