Crossrail chief executive Andrew Wolstenholme is stepping down from his role after seven years leading the £14.8bn project.
The client confirmed that Mr Wolstenholme would be leaving at the end of the month to take on a private sector role.
Crossrail would not disclose details of Mr Wolstenholme’s new role but said his new employer would make an announcement on his appointment in due course.
Mr Wolstenholme will be replaced by Crossrail’s current programme director Simon Wright, who will combine his existing role with that of chief executive.
Mr Wright will oversee the completion of the Crossrail project as the team completes work on the central section of the line and hands over services to Transport for London.
The central section of Crossrail is due to open to services between Abbey Wood and Paddington in December this year.
Crossrail chairman Sir Terry Morgan said: “I would like to thank Andrew Wolstenholme for the phenomenal contribution he has made to the Crossrail project over the last seven years.
“Andrew has overseen the project’s major construction phase including 42 km of new tunnels, 10 new stations and the installation of systems that will support the operation of the new railway.
“He has steered the project with a relentless focus on safety and in a way that delivers wider benefits to the UK in innovation, skills and environmental performance.
“Andrew leaves the team well placed to finish the remaining construction activity and commence infrastructure testing to finish the job, ahead of the opening of the Elizabeth line.”