Dr Who REAL NAME

We will never know. The Doctor knows, and I'm sure some of the other Time Lords may know (the Master, Romana, for example) and River Song knows. But that's about it. We really don't need to know, it's better that way. The name he goes by, the Doctor, sums him up. It's a thing about the Time Lords, they give themselves titles that work for them best.

nobody knows (except possibly River Song), that's one of the things that's always been kept secret to preserve the mystery of the character.