David Tennant announced last October that he would be stepping down from the role at the end of this year, with the new doctor taking over in 2010.
And the person chosen to play the 11th doctor will be announced in a special edition of Doctor Who Confidential, to be aired on BBC1 at 5.35pm.
In a statement implying the new Doctor could be a woman or a man, the BBC said that the actor playing the role would be giving "his or her initial reaction to being the new, 11th incarnation of one of television's most loved characters."
Executive Producer Piers Wenger said: "We are so pleased to have been able to cast this person as the new Doctor.
"We believe the actor is going to bring something very special to the role and will make it absolutely their own - I just can't wait to tell everyone who it is - it has been a nail-biting Christmas trying to keep this under wraps!"
Names in the frame include David Morrissey, who appeared in the Christmas special, Paterson Joseph and Russell Tovey, while some reports have mentioned Martin Clunes and David Walliams.
Writer Russell T Davies has said he would like to see an actress such as Catherine Zeta Jones or play a female Doctor.
This year, there will be four Doctor Who specials featuring Tennant.
