Nanno is an extinct genus of endocerid, named by Clarke in 1894 for the apical end of an endocerid from the Trenton Limestone of New York state that has the basic description of the nanno type. It is possibly a senior synonym for Proterovaginoceras. As a valid genus, Nanno is included in the Endoceratidae, but the nanno type apex may be found in other families.