The event, called Xfm's All Day Breakfast, will feature live music from acts including Paul Weller, Feeder and the Guillemots.
It kicks off at 6am on Saturday June 21 at the Barfly with One Night Only first up, followed by Mystery Jets and Get Cape, Wear Cape, Fly.
Paul Weller will be on at lunch time, while afternoon and evening performances will include Feeder and the Guillemots.
There will be performances into the early hours of Sunday morning, which are yet to be announced, and doors for the last gig will open at 2am.
The whole thing will be broadcast live on 104.9 Xfm London with the best bits going out across the network. Alex Zane, Xfm's breakfast show host, will host the whole event.
Richard Mintz, Xfm marketing director, said: "At Xfm we are always trying to go one better than what we have done before and after last year's 10th birthday gigs we knew it had to be big. The answer? To put all the gigs into one 24-hour period, ensuring a weekend to remember."
Zane said: "I think it's great, I just don't know how you prepare for 24-hours awake, I quite like being in bed at 9.30pm with my mug of hot milk."
Listeners can win tickets to the gig by listening to Xfm London or visiting the .
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