actor-manager who was a leading figure in the development of German theatre.

Conflicting accounts exist of Ackermann's early adult years. He was probably not a trained scientist and surgeon, as has been widely reported, but was instead a soldier—and later an officer—in the Russian army until 1738. He was attracted to the theatre by reading the French playwright Molière and the Scandinavian writer Ludvig Holberg (Holberg, Ludvig, Friherre Holberg). During the years 1740–41 Ackermann received formal acting training in the Lüneburg company of Johann Friedrich Schönemann (Schönemann, Johann Friedrich), who specialized in German adaptations of the French plays of Pierre Corneille (Corneille, Pierre), Jean Racine (Racine, Jean), Molière, and Voltaire.

In 1749 Ackermann married Sophie Charlotte Schröder, the leading lady of Schönemann's company, and with her and a skilled troupe toured Russia, the Baltic states, and East Prussia for many years. It was also during this period that Ackermann was authorized to build an 800-seat theatre in Königsberg; it opened in 1755 and was the first privately owned playhouse in Germany. Soon afterward, however, the Seven Years' War forced Ackermann to move to Switzerland and resume touring.

Gradually Ackermann developed a taste for domestic drama and a technique for acting parts in which he could mingle the comic and the sentimental. In 1765, with the actor and director Konrad Ekhof (Ekhof, Konrad) in his company, he built a modest playhouse in Hamburg. By opening night he was heavily in debt and dissension gripped his company. For the next year he had to lease his theatre, and he did not regain control over it until two years later. Shortly before his death he turned the management over to his stepson, Friedrich Ludwig Schröder (Schröder, Friedrich Ludwig), who was to bring Shakespeare to the German stage.