Barry Robson has been sacked as Aberdeen boss.
Assistant boss Steve Agnew is also leaving.
The decision was made after last night's (January 30) 1-all draw with Dundee at Pittodrie.
Recent league results and performances over the season have been "well below the expectations set", the club say in a statement.
The Dons have won just one of their last five league games.
They sit eighth in the Premiership, only five points behind the relegation play off spot and 18 points behind Hearts who are in third.
Club chaiman Dave Cormack says: "Although it has been a difficult call, the Board felt the change was necessary and in the best interests of Aberdeen FC.
“Barry earned the right to be Aberdeen manager and knew the high level of expectation we had when he took the role. We gave Barry as much time and support as we possibly could in the hope, and expectation, he could return us to the league form we witnessed in the spring of last year.
“There is a talented squad of players at the Club which makes our current league position unacceptable.
“With 17 games left in the league and still in the Scottish Cup, this change is necessary to help us refocus on our ambitions for the rest of the season.
“It’s important we thank Barry for his significant contribution to Aberdeen as a player, a coach and manager. He’s a good man who worked extremely hard in everything he did for us, and it goes without saying that we wish him, and Steve, our very best.
“The Club, as a business, is in good shape. We have no bank debt, significant commercial growth, record season ticket and AberDNA membership sales. We also have an evolving player trading model that is allowing us to invest significantly more in the football operation than the operating income we generate.
“But, as chairman I accept responsibility, along with the board, for the managerial upheavals. It’s exhausting for everyone to go through, not least our fans and the managers who gave their all and lost their jobs.
"We have asked first team coach Peter Leven, assisted by Scott Anderson, to lead training on an interim basis."
Robson took over on a permanent basis just nine months ago, having temporarily taken over in early 2023.
He was awarded the role on a permanent basis after an impressive run of seven consecutive wins.
He led the team to third in the Scottish Premiership and qualification for the UEFA Europa Conference League group stages for the first time in 15 seasons.
In a statement Aberdeen FC added: "The club invested heavily to rebuild the squad during the summer in preparation for a busy schedule on four fronts.
"This helped to produce some extremely credible European performances and progression to the Viaplay Cup Final in December."