The term Black Sun (German Schwarze Sonne), also referred to as the Sonnenrad (German for "Sun Wheel"), is a symbol of esoteric and occult significance. Its design is based on a sun wheel mosaic incorporated into a floor of Wewelsburg Castle during the Nazi era. Today, it may also be used in occult currents of Germanic neopaganism, and in Irminenschaft or Armanenschaft—inspired esotericism—but not necessarily in a racial or neo-Nazi context. Despite its contemporary use, the Black Sun had not been identified with the ornament in Wewelsburg before 1991, although it had been discussed as an esoteric concept in neo-Nazi circles since the 1950s.
The design has loose visual parallels in Migration Age Alemannic brooches (Zierscheiben), possibly a variation of the Roman swastika fibula, thought to have been worn on Frankish and Alemannic women's belts. Some Alemannic or Bavarian specimens incorporate a swastika symbol at the center. The number of rays in the brooches varies between five and twelve.
Goodrick-Clarke (2002) does connect the Wewelsburg design with the Early Medieval Germanic brooches, and does assume that the original artifacts had a solar significance, stating that "this twelve-spoke sun wheel derives from decorative disks of the Merovingians of the early medieval period and are supposed to represent the visible sun or its passage through the months of the year." He further refers to scholarly discussion of the brooches in Nazi Germany, allowing for the possibility that the designers of the Wewelsburg mosaic were indeed inspired by these historical precedents.