The 'Only Girl (In the World) hitmaker will make her only UK performance of 2012 at the London event, topping the bill on the final night of July 8.
Further acts for the festival, which takes place in Hyde Park across three days, are yet to be announced but tickets for Rihanna's headline day go on sale on November 18.
Rihanna - who performed at the dual-site V Festival in Chelmsford, East England and Stafford, West Midlands last year - is currently on her 'Loud' tour of Europe, for which she sold more than 320,000 tickets for the UK leg.
While Rihanna will headline the Wireless festival, she has previously spoken of her desire to top the bill at the legendary Glastonbury Festival.
She has said: "I'd love to play Glastonbury. I have heard so many things about what happens there."
"I know since Jay-Z played at Glastonbury they are open to a lot more R&B. And 'Umbrella' would be the perfect song for that place too."