Matt Smith will be replaced by the 12th incarnation of Doctor Who in a Christmas special.
Smith 30 who took on the role when David Tennant left in 2010 said it had been an honour to play the part.
With no one signed up to replace him Smith's departure immediately raised speculation about whether the next Doctor will be a woman black or both.
Names suggested in newspaper reports include Dame Helen Mirren and Broadchurch star Olivia Coleman with bookmakers offering odds of 8 1 on a female doctor. The Wire star Idris Elba is also gets a mention.
But Harry Potter star Rupert Grint and Russell Tovey of supernatural series Being Human were seen as early 10 1 favourites according to bookmakers William Hill.
The Doctor's current companion played by Jenna Louise Coleman will stay with the show.Russell Tovey and Rupert Grint are among the favourites to be the Doctor
Smith said Doctor Who has been the most brilliant experience for me as an actor and a bloke and that largely is down to the cast crew and fans of the show.
I'm incredibly grateful to all the cast and crew who work tirelessly every day to realise all the elements of the show and deliver Doctor Who to the audience. Many of them have become good friends and I'm incredibly proud of what we have achieved over the last four years.
He also paid tribute to show supremo Steven Moffat whose varied funny mind bending and brilliant scripts has been one of the greatest and most rewarding challenges of my career .
He said It's been a privilege and a treat to work with Steven he's a good friend and will continue to shape a brilliant world for the Doctor.Matt Smith has a friendly encounter with the Doctor's great enemy a Dalek
The fans of Doctor Who around the world are unlike any other they dress up shout louder know more about the history of the show (and speculate more about the future of the show) in a way that I've never seen before your dedication is truly remarkable.
Thank you so very much for supporting my incarnation of the Time Lord number Eleven who I might add is not done yet I'm back for the 50th anniversary and the Christmas special.
Smith who recently made his directorial debut has spoken about ambitions for a film making career.
While playing the Doctor he has also taken on other roles including the novelist Christopher Isherwood and 1948 Olympic rower Bert Bushnell.
He has recently been filming a lead role in the Ryan Gosling film How To Catch A Monster which is due out next year.
Moffat said Every day on every episode in every set of rushes Matt Smith surprised me the way he'd turn a line or spin on his heels or make something funny or out of nowhere make me cry I just never knew what was coming next.Smith the youngest actor to win the part took over from David Tennant
But great actors always know when it's time for the curtain call so this Christmas prepare for your hearts to break as we say goodbye to number Eleven. Thank you Matt bow ties were never cooler.
Smith is due to appear with Tennant Billie Piper Jenna Louise Coleman and John Hurt in Doctor Who's 50th anniversary special before his farewell episode at Christmas.
Moffat added Of course this isn't the end of the story because now the search begins.
Somewhere out there right now all unknowing just going about their business is someone who's about to become the Doctor. A life is going to change and Doctor Who will be born all over again After 50 years that's still so excitingRelated stories Tennant And Piper Back For Doctor Who's 50th Gillan Warns Of Tearful Parting From Doctor Doctor Who Stars Storm National TV Awards