A brand new story about boy wizard Harry Potter is up for sale - but not in bookshops!
The 800-word tale was written by JK Rowling for a charity auction to help people with reading problems.
The handwritten story is secret, but it's about Harry's life before the first Potter book.
Bidding is expected to go mad for the unique tale, which is written on a sort of postcard. But don't worry, it will be published later in August.
In December, JK Rowling's handwritten book of short stories about Harry's world - Tales of Beedle the Bard - raised £1.95 million for charity.
JK Rowling is one of 13 authors helping charity
Auction expert Philip Errington said it looked like this work would notch up the cash too, adding: "There is just no telling how high the bidding might go."
JK was one of 13 authors asked to write something for the charity auction and all their work will be published in one book.
JK adds at the end of her writing: "From the prequel I am not working on - but that was fun!"