(from Greek chrysoboullon, gold seal), a type of official document in the Byzantine Empire. The chrysobull differed from other types of official documents in the manner in which it was drawn up. The emperor himself wrote several words in purple ink and then signed and dated the document. The chrysobull was authenticated with a seal on a silk cord; the seal was sometimes made of gold. Laws, treaties with foreign powers, and charters of great importance were promulgated in the form of chrysobulls. The extant chrysobulls are, for the most part, copies.
The chrysobull was also used in the chancelleries of medieval Bulgaria and Serbia.