The Old English Martyrology is one of the longest and most important prose texts written in Anglo-Saxon England; it also represents one of the most impressive examples of encyclopaedic writing from the European Middle Ages. Probably intended as a reference work, it experienced more than 200 years of transmission and usage. Its principal aim must have been to educate Anglo-Saxon readers in their cults of native and foreign saints, but it also presents detailed information on time measurement, the seasons of the year, biblical events, and cosmology. Its range is impressive even by modern standards: the text makes reference to roughly 450 historical and legendary characters, covering more than 6000 years of political, ecclesiastical and saintly history, as the events described range from the creation of the world in the year 5199 before Christ to contemporary cosmological phenomena still observed by the author himself. Geographically, the text covers the British Isles to western, central, and southern Europe, the Middle East, Northern Africa, and India. The complete set of data contained in this encyclopaedia is collected in no other surviving literature from the early Middle Ages, although constituent parts of this information can be found in some 250 earlier texts, many of which may directly have influenced the composition of the Old English Martyrology. It is hard to imagine today what difficulties its author or authors must have overcome in the compilation of this knowledge, and even now, in an age where information travels fast and electronically, one is struck by the range and comprehensive nature of this hagiographical database.