The Sworn Book of Honorius, also known by its Latin title Liber Juratus Honorii, is one of the important surviving works of medieval ceremonial magic. Its precise date of composition remains uncertain, although the text was circulating by the Middle Ages and survives in manuscripts dating from the fourteenth century onwards.

The work presents itself as the product of a gathering of eighty-nine masters of magic who resolved to preserve their knowledge at a time when magical books were supposedly threatened with destruction. According to its own narrative, their teachings were condensed into a single volume by a master named Honorius. This account belongs to the text's legendary framework and should not be treated as a documented historical event.

At the centre of the book is an elaborate system of ritual and devotional magic. Its instructions combine prayer, purification, sacred names, invocations and the construction of the Sigillum Dei, or Seal of God. Among its highest aims is the attainment of a vision of the divine, alongside knowledge of angels and other spiritual beings.

The text also describes extensive hierarchies of angels and spirits and provides instructions relating to their invocation. Its magical operations address both spiritual and practical objectives, placing ceremonial procedures within a strongly Christian theological framework. Surviving manuscripts contain prayers, lists of angelic names, ritual instructions and diagrams associated with these operations.

The word juratus refers to the oath-bound character of the book. Its own instructions place restrictions on how the knowledge should be transmitted, presenting magical learning as something entrusted only to selected practitioners under conditions of secrecy.

For modern readers, The Sworn Book of Honorius provides an important example of medieval ritual magic in which Christian devotion, angelology and ceremonial practice exist alongside traditions of spirit invocation.