A Brocken spectre (German Brockengespenst), also called Brocken bow or mountain spectre, is the apparently enormous and magnified shadow of an observer, cast upon the upper surfaces of clouds opposite the sun. The head of the figure is often surrounded by the glowing halo-like rings of a glory—rings of colored light that appear directly opposite the sun when sunlight meets a cloud of uniformly-sized water droplets.

The phenomenon can appear on any misty mountainside or cloud bank, even when seen from an aeroplane, but the frequent fogs and low-altitude accessibility of the Brocken, a peak in the Harz Mountains in Germany, have created a local legend from which the phenomenon draws its name.