The chief executive of Network Rail, John Armitt, is to retire at the end of July 2007.
Network Rail reported its first profit last month
Mr Armitt said the time was "right to move on" after what he said had been "five challenging, enjoyable and successful years".
He will be replaced by Iain Coucher, who has been deputy chief executive of Network Rail since October 2002.
Network Rail took over the running of the UK's railway tracks and signals from Railtrack in 2002.
Last month, it unveiled its first profit - £747m for the six months to September.
Network Rail chairman Ian McAllister said Mr Armitt had been an "outstanding" chief executive.
"He took over at a time when the railway had considerable problems and he has successfully led the team as we have stabilised the company, delivered a substantial improvement in the punctuality of trains and the cost efficiency of the railway," he said.