Union Berlin have announced the "painful" departure of manager Urs Fischer following a joint decision.
Union are in their fifth successive Bundesliga season since Swiss Fischer, 57, achieved their first promotion to Germany's top tier in his debut season.
The fan-owned club qualified for Europe in each of the past three seasons and this year competing in the Champions League for the first time.
However, Union is bottom of the Bundesliga after 11 games this season.
"This is a very sad moment not only for me personally but certainly for the entire Union family," said Union president Dirk Zingler.
"It hurts that we have not managed to break the negative run of recent weeks. I am grateful and proud when looking back on the time we have spent and the successes we have celebrated together.
"As painful as this separation is, Urs Fischer is leaving as a friend who will always be welcomed by us with open arms."
Fischer, who took charge in 2018, led Union to 11th in their first Bundesliga season.
They finished seventh, fifth and fourth between 2021 and 2023, reaching the Europa Conference League, Europa League and Champions League - each for the first time in their history.
Union have lost nine league games this season and are without a victory in 14 in all competitions since winning their first two Bundesliga matches in August.
"The last few weeks have cost a lot of strength," said Fischer.
"We've tried a lot, and the team has put in a lot of effort, but it hasn't paid off in terms of results.
"I am very grateful for the confidence I have always felt here. Nevertheless, it feels right to make a change now.
"I wish Union all the best and am convinced that they will manage to stay in the league."
