Mainz sacked head coach Achim Beierlorzer on Monday after just two games of the new Bundesliga season.
Beierlorzer has overseen two defeats in those two games, the second on Saturday when Mainz were thrashed 4-1 at home by newly-promoted Stuttgart.
The 52-year-old manager arrived at Mainz in November 2019 and successfully led the club away from potential relegation last season.
Assistant coach Jan-Moritz Lichte will take charge of the side until further notice.
Beierlorzer’s sacking is the second in as many days, Schalke having shown David Wagner the door on Sunday.