And it won't be a small affair either - the party is said to be costing around £55,000.
So, is this generous gesture from Her Majesty proof she's put all those scandalous Fergie headlines behind her?
The Express reports Prince Andrew's former wife has invited 300 guests to her birthday celebrations at Windsor's State Apartments on Wednesday.
A royal source told the newspaper, "The Duchess of York is over the moon that the Queen allowed her to hold the party at the castle, and she hopes many of her friends can make it.
"We are expecting lots of big names. Everyone wants to see if Prince Harry and Cressida turn up as a couple. The Duchess's charities also want to pay tribute to her many years of work and lots of them will be here as well."
As for the Duke and Duchess of Cambridge making an appearance? They've been sent an invitation, however, the royal couple are unlikely to attend as the pregnant duchess is still suffering from morning sickness.
That said, there's a whole host of celebs set to attend: Sir Elton John and David Furnish, Stephen Fry, Robbie Williams, Sir Richard Branson, Formula One boss Bernie Ecclestone and his daughters Tamara and Petra, plus Naomi Campbell and Kate Moss.
Pretty good going for a guest list, no?
LOVE FERGIE? See more of the Queen's former daughter-in-law below: