The Tau Emperor (Aglia tau) is a moth of the family Saturniidae. It is found in Europe. The wingspan is 60–84 mm. The moth flies in one generation from March to July depending on the location. The larvae primarily feed on European Beech, but also Birch, Alnus glutinosa, Salix caprea and Sorbus aucuparia. The larvae look rather like hickory horned devil caterpillars in the early instar