Georg Theodor Ziehen (12 November 1862 – 29 December 1950) was a German neurologist and psychiatrist born in Frankfurt am Main. He was the son of noted author, Eduard Ziehen (1819–1884). As a gymnasium student he studied the works of Immanuel Kant and Arthur Schopenhauer at Lessing-Gymnasium in Frankfurt. Later he studied medicine in Würzburg and Berlin, where he received his doctorate in 1885. While a medical student he studied the writings of David Hume, Spinoza, Plato and George Berkeley. Following graduation he worked as an assistant to Karl Ludwig Kahlbaum at the mental hospital in Görlitz, and in 1887 became an assistant to Otto Binswanger at the psychiatric clinic in Jena. At Jena one of his patients was philosopher Friedrich Nietzsche.