What is the Doctor's real name?

Question

Is there anywhere (in canon) where the Doctor's real name is ever revealed? I know that several people do know it or learn it at some point (like the Master, River, and Clara for example), but is it ever revealed to us?

Answer 1

The Doctor's name is unknown.

The true name of Doctor Who is one of the great mysteries of the series (e.g. see here).

Steven Moffat, the executive producer, has said the Doctor's real name is Mildred, but this is generally assumed to be a joke. (Rule #0: the Moffat lies.) In Series 9, the Doctor tells Osgood that his first name is Basil, but this is presumably also a joke. (Rule #1: the Doctor lies.)

In Series 10, it is claimed that his real name is Doctor Who:

BILL: So, why do you keep calling yourself Doctor Who?
MISSY: Because I'm pretending to be him. Because that's the whole point of this ridiculous exercise.
[...]
BILL: Yeah, but he's called the Doctor, so
MISSY: He says, I'm the Doctor, and they say, Doctor who? See, I'm cutting to the chase, baby. I'm streamlining. I'm saving us actual minutes.
BILL: Yeah, okay, whatever.
MISSY: Also it's his real name.
[...]
BILL: Sorry, what do you mean, it's his real name? Nobody knows the Doctor's real name.
MISSY: I do, because I grew up with him, and his real name is Doctor Who.
DOCTOR: Bill, she's just trying to wind you up.
MISSY: Chose it himself, you know, trying to sound mysterious. And then he dropped the Who when he realised it was a tiny bit on the nose.

_{-- S10E11 (World Enough and Time)}

Again, I would assume that this isn't actually true. (Rule #2: the Master lies.) If the Doctor's name really is such an earth-shattering secret as it was made out to be in Series 6, then it would hardly be the thing everyone says as soon as they meet him. Nor would the question broadcast from Trenzalore in "The Time of the Doctor" make sense if that question was actually his real name.

Answer 2

While we may not know his actual name, we do know he went by Theta Sigma while at the Time Lord Academy on Gallifrey and it is the answer to the question, Doctor Who? That must never be answered.

Some have suggested that maybe Theta Sigma is his name or short for what his name really is. I don't believe we will ever get the answer to that. However, it has been said that only children can hear his name. But that doesn't necessarily mean they can understand his name.

See “The Armageddon Factor” and “Happiness Patrol” on the name Theta Sigma. Drax called him Theet. Short for Theta Sigma.

Come on, Theet. Class of ninety two?

Yeah. We was on the tech course together. Long time ago now, Theet, eh? Must be what, four hundred and fifty years? And a long way from Gallifrey.

_{The Armageddon Factor, Part Six.}