The rapper is topping the bill at the world famous music event on the Saturday night (28.06.08) - much to the anger and disappointment of many fans - but organiser Michael Eavis has confessed Jay-Z wasn't his first choice.
He said: "I was working on getting Radiohead and I had a feeling they wanted to do it but, when it went down, I said to my daughter Emily, 'Let's go with Jay-Z. Phone his agent.' "
Emily - who helps her father organise the three-day music event - has defended Jay-Z as a choice of headliner, insisting it fits with the festival's ethos.
She told Britain's The Sun newspaper: "People don't want change and there's an element who want it to be a Coldplay or Radiohead - but the best thing we can do is give people something different.
"A lot of people don't understand why Jay-Z is headlining but they haven't seen him live. He is phenomenal. Every time someone comes to this festival they discover new music - this year it will be a headliner."
Emily and Michael have been saddened by the avalanche of criticism over this year's line-up, with Emily saying: "It's upset us having to defend the festival this year. It's our home, we invite people here and it's the best party in the world."
Michael added: "This has been our life for 38 years, so of course it hurts when people have a go."
Glastonbury festival takes place in Somerset, Southwest England, over the weekend of June 27-29, and Radiohead kick off the European leg of the In Rainbows Tour tonight in Ireland before heading back to do a 2nd North American leg in August.
Kings of Leon and The Verve join Jay-Z as headliners.