Charles Augustus may refer to:
Karl August, Grand Duke of Saxe-Weimar-Eisenach (1757–1828) Charles Augustus, Hereditary Grand Duke of Saxe-Weimar-Eisenach (1912–1988) Charles Augustus, Hereditary Grand Duke of Saxe-Weimar-Eisenach (1844–1894) Charles Augustus, Prince of Nassau-Weilburg (1685–1753)