Book experts have no idea where they are now, but say they are worth loads of galleons, sickles and knuts.
Back in 1997 when the book first came out, you could pick up a copy for £10.99.
But now if you sold your first edition, it would go for about £16,000. And if it's signed by JK herself, it could make £20,000!
But be warned - there are loads of internet auction sites advertising first editions for sale. But it's hard to spot fakes on the net!
Make sure you know how to spot a fake by checking out our tips to the right of this story.