Hans Georg Hermann von Plessen (26 November 1841 – 28 January 1929) was a Prussian Colonel General (German: Generaloberst) and Canon of Brandenburg who held the honorary rank of Generalfeldmarschall in his role as Commandant of the German General Staff during World War I.General von Plessen also held the office of His Majesty's Orderly Adjutant General (German: SM diensttuender Generaladjutant) to Kaiser Wilhelm II, thus making him one of the Emperor's closest confidants.
By 1918 he was the oldest serving officer in the Imperial German Army, although Paul von Hindenburg falsely claimed this for himself.