The US star will perform at London's Wembley Stadium on June 9 as part of the annual music event.
Further acts are expected to be announced tomorrow (April 21), with tickets to be released on Monday April 23 from 8am.
Speaking about this year's show, Capital Breakfast Show presenter Dave Berry said: "As if presenting to a packed Wembley wasn't enough to get me going, I've now heard the genuinely amazing lineup for this year's show.
"I've been sworn to secrecy by Capital, but I'm not sure how long I'll be able to keep it quiet on air."
Last year's show saw performances from Jennifer Lopez, Cee Lo Green, Ne-Yo, The Wanted, Nicole Scherzinger and Enrique Iglesias.
> Kelly Clarkson covers Britney Spears's 'Til the World Ends' - video
Watch the music video for Kelly Clarkson's 'Stronger' below: