The Head Coach has left the club with immediate effect.
In a statement, the club say: "Barnsley Football Club confirms that it has separated from Daniel Stendel with immediate effect.
Adam Murray has been appointed caretaker manager."
It follows a run of ten league games without a win.
The German was appointed in June 2018, and led the club to promotion in his first season, including an unbeaten league campaign at Oakwell.