Abstract: A novel mouth whistle capable of a very loud whistle sound and comfortable to hold and use orally is shaped with a somewhat flattened hemi-oblate body with a cavity opening to the front, the back end being rounded and the front opening end being cut off substantially flat in a single plane, transverse to the upper and lower opposed walls defining the cavity. The upper and lower walls are each perforated with a single, centrally located aperture substantially coaligned and in communication with the cavity.