Friedrich August, Hereditary Prince of Saxe-Eisenach

Friedrich August, Hereditary Prince of Saxe-Eisenach 30 October 1663 - 19 September 1684) was the heir of Saxe-Eisenach but never acceeded to the title of Duke of Saxe-Eisenach. He was the son of Johann Georg I, Duke of Saxe-Eisenach. He wis also a brother of Princess Eleonore Erdmuthe of Saxe-Eisenach, the mother of the future Caroline of Ansbach.