The sixth Harry Potter book will hit the shops on 16 July next year, it has been announced.
JK Rowling is expecting her third child next year
Harry Potter and the Half-Blood Prince will be published simultaneously in the
UK, the US, Canada, Australia, New Zealand and South Africa.
Author JK Rowling revealed on Tuesday she had completed the novel after originally saying she would announce details on Christmas Day.
The new book is sure to spark a frenzy among fans of the teenage wizard.
The release date for Harry Potter and the Half-Blood Prince was revealed by Rowling's UK publisher Bloomsbury.
Their shares surged 7% to a new all-time high of £2.94 after Rowling revealed she had completed the novel.
Harry Potter and the Half-Blood Prince takes up the story of Harry Potter's sixth year at Hogwarts School of Witchcraft and Wizardry as Lord Voldemort grows stronger.
Rowling has already revealed that the Half-Blood Prince is neither Harry nor Voldemort.
And she added that the opening chapter of the book has been brewing in her mind for 13 years.
Rowling said she had plenty of time while pregnant "to tinker with the manuscript to my satisfaction and I am as happy as I have ever been with the end result".
Writing on her website, Rowling said: "I know you all expected this to happen on Christmas Day.
"But I was sure that those of you who celebrate Christmas have better things to do on the day itself than fight your way into my study, whereas those of you who don't celebrate Christmas would definitely prefer not to wait until the 25th."
Rowling has also previously revealed that a character will be killed in the sixth book, but she has given no hints as to whom.
In a statement, Nigel Newton, chief executive of Bloomsbury in the UK and Barbara Marcus, president of Scholastic Children's Books in the US, said: "JK Rowling has written a brilliant story that will dazzle her fans in a marvellous book that takes the series to yet greater heights.
"Harry Potter and the Half-Blood Prince delivers all the excitement and wonder of her bestselling Harry Potter novels."
The fifth book, Harry Potter and the Order of the Phoenix, was published in June 2003.
The series has been a publishing phenomenon, with five million copies of the last book sold in the first 24 hours of publication.
Fans had to wait three years between publication of the fourth and fifth books.
Each book has got longer and longer, with Harry Potter and the Order of the Phoenix reaching 870 pages. Rowling has said there will be seven novels in the series.
Rowling gave birth to her second child in 2003 and is expecting her third next year.