A Golden Bull or chrysobull was a golden ornament representing a seal (a bulla aurea or "golden seal" in Latin), attached to a decree issued by Byzantine Emperors and later by monarchs in Europe during the Middle Ages and Renaissance. The term was originally coined for the golden seal itself but came to be applied to the entire decree. Such decrees were known as golden bulls in western Europe and chrysobullos logos, or chrysobulls, in the Byzantine Empire (χρυσός, chrysos, being Greek for gold). Golden bulls originated in the Byzantine Empire, for which they served as a particularly important diplomatic tool. The empire's official ideology rested on the idea that the Byzantine Emperor was chosen by God to be the ruler of the world's only legitimate empire. The Byzantines were remarkably successful in persuading other states to accept this, presenting golden bulls as acts of imperial grace but using them as de facto treaties without having to admit that foreign powers had any equal standing. They were also a useful means of enabling the empire to maintain the fiction that even humiliating concessions to powerful neighbours were really nothing of the sort. For nearly eight hundred years, they were issued unilaterally, without obligations on the part of the other party or parties. However, this eventually proved disadvantageous as the Byzantines sought to restrain the efforts of foreign powers to undermine the empire. During the 12th century, the Byzantines began to insert into golden bulls sworn statements of the obligations of their negotiating partners. Other European monarchs adopted golden bulls in imitation of the Byzantines, but used them much more sparingly. The exceptional nature of non-Byzantine golden bulls gave them a much higher profile than either the Byzantine originals or ordinary proclamations. Notable golden bulls included:
- The Golden Bull of 1136, issued by Pope Innocent II, more commonly known as the Bull of Gniezno.
- The Golden Bull of Sicily, issued by 1212 by Frederick II, Holy Roman Emperor.
- The Golden Bull of 1213, issued by Frederick II, Holy Roman Emperor.
- The Golden Bull of 1214, issued by Frederick II, Holy Roman Emperor ceding all German territories north of the rivers Elbe and Elde to King Valdemar the Victorious of Denmark.
- The Golden Bull of 1222, issued by King Andrew II of Hungary. This confirmed the rights of the nobility; it was forced on him much in the same way that King John of England was made to sign the Magna Carta.
- The Golden Bull of 1224 (the Goldenen Freibrief) was also promulgated by Andrew, granting certain rights to the Saxon inhabitants of Transylvania.
- The Golden Bull of Rimini (1226), issued by Frederick II, Holy Roman Emperor.
- The Golden Bull of Berne, supposedly also issued by Frederick II in 1218, but now considered a forgery.
- The Golden Bull of 1267, issued by King Bela IV of Hungary.
- The Golden Bull of 1348, issued by King Karel I of Bohemia, later Holy Roman Emperor as Charles IV, to establish Charles University in Prague, one of the oldest universities in the world.
- The Golden Bull of 1356 is probably the most famous golden bull, being a decree issued by the Holy Roman Emperor Charles IV. Its promulgation at the Diet of Nuremberg defined, for a period of more than four hundred years, the constitutional structure of the Holy Roman Empire.
- The Golden Bull of 1702, issued by Leopold I, Holy Roman Emperor to establish the Akademia Leopoldina in the Silesian capital of Breslau (present name: Wrocław), the future University of Breslau (Universitas Vratislatensis).
