Derek McInnes has left Aberdeen after eight years in charge of the Scottish Premiership side.
McInnes took over the reins at Pittodrie in March 2013 and steered the Dons to their first trophy in two decades with their Scottish League Cup win in 2014.
Aberdeen are currently fourth in the Scottish Premiership table, three points behind third-placed Hibernian but having scored just once in their last nine games.
In a club statement Aberdeen confirmed the departures of McInnes and his assistant Tony Docherty with immediate effect.
Dons chairman Dave Cormack said in a statement: “During his time in charge Derek raised the bar and delivered a level of consistency not seen at the club for many years, qualifying for Europe each season, and delivering a memorable Scottish League Cup win at Celtic Park in season 2013-14 with 43,000 Dons fans in attendance.
“Clearly, results since the turn of the year have been disappointing and frustrating for everyone.
“Derek and I reviewed where we were and agreed that this was the right time for him to step down.”