Friedrich Eckstein (February 17, 1861, in Perchtoldsdorf, Lower Austria - November 10, 1939, in Vienna) was an Austrian polymath, man of letters, Theosophist and a friend and temporary co-worker of Sigmund Freud. He taught S. Freud the Yoga.
He was also the husband of fellow theosophist and writer Bertha Diener.