JK Rowling, author of the Harry Potter novels, is celebrating the arrival of her third child.
The couple married in 2001
The baby girl, who has not yet been named, was born on Sunday evening, a spokesperson for Rowling exclusively told the BBC's Newsround programme.
Rowling and her husband, Dr Neil Murray, are said to be "thrilled" at the birth.
The baby is the second child for the couple. The author also has a daughter from a previous marriage.
Last year Rowling told fans on her website that she always wanted three children and "could not be happier".
Rowling announced late last year that the sixth Harry Potter book will hit the shops on 16 July.
Harry Potter and the Half-Blood Prince will be published simultaneously in the UK, the US, Canada, Australia, New Zealand and South Africa.