Dietrich Gerhard Emil Theodor Tappen (3 July 1866 – 28 May 1953) was a German World War I general.

At the start of the First World War, Tappen was a colonel in the Oberste Heeresleitung (OHL) in Koblenz, where he led the operations section which coordinated the German battle strategy.

[1] In September 1914 Tappen reported from a tour of inspection at the front that the French were too exhausted to begin an offensive, that a final push would be decisive and that more withdrawals would compromise the morale of the German troops, after the defeat on the Marne.

[2] In March 1915 Tappen served as chief of staff of the 7th Army under Josias von Heeringen, but soon returned to OHL.

On 31 August 1916 Tappen was transferred out of OHL and became chief of staff to Army Group Mackensen on the Romanian front.