Dutchman Jan Olde Riekerink was appointed as manager in March 2016 and leaves the club in third place on the Super league table five points behind log leaders, Besiktas.
Turkish football club Galatasaray on Tuesday parted ways with head coach Jan Olde Riekerink less than a year after the Dutchman took the position, club President Dursun Ozbek announced.
Riekerink led the club to a domestic cup win over bitter rivals Fenerbahce last year, but Galatasaray are currently in third place and five points behind league leaders Besiktas after 20 games.
The club failed to qualify for the UEFA's Champions League and Europa League this season after finishing the 2015-16 season in sixth place.
The news comes a day after Galatasaray suffered a 2-1 home loss to Kayserispor, a team flirting with relegation.
The announcement was made official at a board meeting on Tuesday despite disagreements within the board.
The Dutch manager was appointed as manager in March 2016 after the team parted ways with prominent Turkish manager Mustafa Denizli last February.
Galatasaray is replacing Riekerink with Super League team Kardemir Karabukspor's Croatian Manager Igor Tudor.
Kardemir Karabukspor's Chairman Ferudun Tankut told Anadolu Agency that Tudor had already agreed to terms with Galatasaray.
"Tudor will leave the club tomorrow for Galatasaray," Tankut said, adding, "This is not ethical at all. Galatasaray never contacted me on the issue."