Speaking to the Daily Star, the 29-year-old said: "I'm a massive fan of Madonna. I've been a fan of hers for years. She's a real artist."
However, Gillespie Sells admitted that he would be intimidated if he met the pop icon backstage.
He said: "She scares me. There are some people I'd go talk to and I'd know what to say. But with someone like her I wouldn’t really know what to say."
The two-day Big Weekend event takes place at Mote Park, Maidstone, Kent today and Sunday. Usher, Duffy, Robyn and The Kooks are also on the bill.