JK Rowling has amassed a £540m fortune from writing
It will be called Harry Potter and the Deathly Hallows. The announcement was made on the writer's official website.
Despite the publication date not being known, the book is tipped to be a big seller, like the rest in the series.
Speculation about the plot has surrounded the book after Rowling admitted two characters will die - some think it could be Harry Potter himself.
'Elated and overwrought'
The title has certainly got some fans excited.
Harry, 13, from Leicestershire emailed BBC Newsround and said: "It sounds interesting, but a bit sinister."
Book chain Waterstone's children's buyer, Sam Harrison, said the announcement had been greeted with "huge excitement" among Potter fans.
"This is a wonderfully intriguing and ominous title, with all the sense of magic and adventure that any true Potter fan has come to love and expect," Harrison added.
I'm now writing scenes that have been planned, in some cases, for a dozen years or even more
JK Rowling
The last book, Harry Potter and the Half-Blood Prince, broke UK records by shifting just over two million copies on its first day of release.
Sales of all Harry Potter titles now total more than 52 million worldwide.
This week Rowling revealed how she has gone back to writing in cafes - as she did 13 years ago when starting to write about the boy wizard.
She has also admitted how she has been dreaming of the character.
Writing on her website she described it as an "epic dream" where she was Harry and the narrator simultaneously.
THE HARRY POTTER SERIES Harry Potter and the Philosopher's Stone (Harry Potter and the Sorcerer's Stone in the US) Harry Potter and the Chamber of Secrets Harry Potter and the Prisoner of Azkaban Harry Potter and the Goblet of Fire Harry Potter and the Order of the Phoenix Harry Potter and the Half-Blood Prince
In a recent web posting, she said she has been working hard on the last book.
"I'm now writing scenes that have been planned, in some cases, for a dozen years or even more," she said.
She also described feeling "alternately elated and overwrought" at writing it and joked she cannot decide if she wants to finish it or not.
The first four novels in the series have been turned into films, while the fifth, Harry Potter and the Order of the Phoenix, is currently in production and is due for release in July 2007.
Helena Bonham Carter joins the cast as the evil Bellatrix Lestrange and Imelda Staunton will play the part of dark arts teacher Dolores Umbridge.
British author J.K. Rowling has revealed the title of the seventh and final book in the Harry Potter series in an online game on her official website. Contenders would click on items to reveal a chamber, then they would use the clues given and guess the title. After fans played a game they were rewarded with the title of the book which is to be called ''Harry Potter and the Deathly Hallows''. She also revealed that Harry had been taking place in her dreams and she was returning to writing in cafes, as she did 13 years ago.

"One character got a reprieve but I have to say that two die that I didn't intend to die," Rowling, 41, said June 27 on ''Richard & Judy'', a television show run in the U.K.

The book is first published in the U.K. by London-based Bloomsbury and then sent to the U.S. by Scholastic Corp.

"I'm writing scenes that have been planned, in some cases, for a dozen years or even more," Rowling wrote on her website. "I don't think anyone who has not been in a similar situation can possibly know how this feels: I am alternately elated and overwrought. I both want, and don't want, to finish this book (don't worry, I will)."

The film version of ''Harry Potter and the Order of the Phoenix'', the fifth book in the series published June 21, 2003, is still in production and will be released in July 2007.

Rowling was inspired to write after her mother died from multiple sclerosis in 1990 and after a marriage breakdown. She started writing in Edinburgh cafés. Whenever her daughter Jessica fell asleep she would put her in a carriage beside her and stroll her to the closest café. 300 million books worldwide have been sold and the series has been translated into 47 languages.

No publication date has been set.