Julius Ernst von Tettau (July 16, 1644 – June 22, 1711) was a Brandenburg-Prussian subject serving in the Dutch, French, Danish, and Brandenburg armies, reaching general officers rank in Danish, Brandenburg, and Dutch service.

Tettau served as fortress builder, but also as tutor for the Kurprinz, the later King Frederick.

In 1689 he became Major-general of Foot in the Danish Auxiliary Corps in Ireland, distinguishing himself at the sieges of Cork, Kinsale, Athlone, and Limerick.

Distinguishing himself in Flanders, he was wounded in action at the battle of Steenkerque 1692, and advanced to Brandenburg Lieutenant-general and Dutch Generalfeldzeugmeister.

At the end of the war, he returned to East Prussia, where he had large estates, distinguishing himself in civilian service.