A Brocken spectre (British English; American spelling: Brocken specter; German: Brockengespenst), also called Brocken bow, mountain spectre, or spectre of the Brocken is the magnified (and apparently enormous) shadow of an observer cast in mid air upon any type of cloud opposite a strong light source. Additionally, if the cloud consists of water droplets backscattered, a bright area called Heiligenschein, and halo-like rings of rainbow coloured light called a glory can be seen around the head or apperature silhouette of the spectre. Typically the spectre appears in sunlight opposite the sun's direction at the antisolar point.

The phenomenon can appear on any misty mountainside, cloud bank, or be seen from an aircraft, 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. The Brocken spectre was observed and described by Johann Silberschlag in 1780, and has often been recorded in literature about the region.