Sir Jeremy Fleming is to stand down as the director of GCHQ after six years in the role.
The spy chief, who is the 16th person to head up the UK’s intelligence, cyber and security agency, will end his tenure in the summer.
The recruitment process to find his replacement is under way.
“Sir Jeremy Fleming, director GCHQ, has today announced his decision to step down at the end of his tenure later this year,” GCHQ said in a statement.
“In line with normal practice, there will be an internal civil service competition to identify a successor. Sir Jeremy and the board will continue to lead and oversee work at GCHQ until the summer.”
Sir Jeremy, who joined MI5 in 1993, has most recently spoken out on Russian President Vladimir Putin’s “flawed” decision-making during his invasion of Ukraine.
He also warned of the “dangerous” talk of nuclear weapon use during the conflict, while paying tribute to Ukrainian cyber security personnel, and pledged continued support.
Despite the potential immediate threat posed by Russia, Sir Jeremy previously warned in an interview of China’s use of technology to attack satellite systems, control digital currencies, and to control dissent by tracking individuals.
He told BBC Radio 4’s Today programme that China was the “real long-term threat” to UK national security – claiming the country was “deploying its ideologies in ways that we think are against our national interests”.
Sir Jeremy also spoke out about the increased threat of cyber attacks during the coronavirus pandemic, with GCHQ supporting the health sector as vaccine research was targeted by hackers.