The pop singer said Friday she cannot wait to perform. She says: "I'm pumped just thinking about that huge audience and soaking up their energy."
She joined about 140,000 music fans at the festival in southwest England's Somerset in 2008 to see Jay-Z's show.
Last year's headline acts included Stevie Wonder and Gorillaz, a last-minute replacement for U2 who were forced to cancel after singer Bono suffered a back injury.
The outdoor festival, one of the largest and best-known of its kind, celebrated its 40th anniversary last year. Tickets for this year's event on June 22-26 already have sold out.