Martin O'Neill has left his post as manager of Nottingham Forest, the Championship club have announced.
The 67-year-old, who was appointed at the start of the year, spent 10 years at the City Ground and made more than 300 appearances and scored more than 50 goals for the club.
O'Neill first signed for Nottingham Forest for £15,000 in 1971.
He played in Forest's 1980 European Cup final victory against Hamburg.
As a manager he won the League Cup with Leicester City and guided Celtic to three Scottish Premiership titles.
In a statement, Nottingham Forest said: "The club would like to thank Martin for all his efforts during his time at The City Ground and wish him well for the future."
The club has also announced Sabri Lamouchi has been appointed as Nottingham Forest's new head coach.