Beathat230.jpgIt was the hat heard 'round the world, so to speak - Princess Beatrice's hat (right) at the royal wedding turned heads and made headlines, and now it's up for sale.

Beatrice, 22, cousin of Prince William, got the hat from famed London milliner Philip Treacy. He is a favorite of Kate Middleton's and made hats for dozens of the guests.

Now Beatrice plans to put the cap on eBay and auction it for UNICEF and "for children in crisis," said her mother, Duchess Sarah Ferguson, on Oprah Wednesday.

Treacy's hats can cost thousands of dollars ... we wonder how much Beatrice's topper will fetch. We can't imagine an occasion for anyone to wear it ...

Fergie, who caused a scandal last year when she was caught on tape selling out her ex-husband, Prince Andrew, was not invited to the royal wedding. See what she told Oprah about the snub after the jump!