Martin George said the post, which he will assume on Wednesday, was his “dream job”.
He was a pupil at the school between 1975 and 1980. One of his former teachers – John Curry, head of physics – is still working there.
Mr George said: “If you know anything about Durham School, you know it’s a big, extended family. It always has been and that’s a great attraction.
“It’s like coming home. It’s almost like I’ve been away for the last 29 years, but now I’m home.
“It’s a pleasure and a privilege to return. I’ve got to get to know it again, but the overriding emotion is one of enormous excitement.
“The school meant so much to me as a pupil.”
Mr George is currently deputy headmaster with responsibilities for pastoral issues at The King’s School, in Tynemouth.
At Durham, he succeeds Neil Kern, who retired as headmaster last summer after 11 years in the job.
The 46-year-old said he wanted to increase the number of pupils boarding at the school, currently about a fifth of the total, and see the school excel in everything it did.
Mr George lives in Whitley Bay with his wife Vivienne, 48, and children Max, 12, and Claudia, ten, although his new job comes with use of a home, in Durham’s South Street.
A former Army officer, he has also taught in Newcastle-under-Lyme. His interests include music, theatre, sport and outdoor pursuits such as running, fell walking and skiing.
He said, despite the deepening recession, the school was receiving a high number of inquiries from parents.
“Of course, inquiries have got to turn into registrations and pupils coming through the doors.
“I think the current climate is a threat, but it’s also an opportunity to look at what you do and sell what you do.
“You’ve got to be sure what you’re offering is value for money.”