Byrhtferth

thumb|Byrhtferth's diagram with the Four elements (earth, water, air, fire), seasons, solstices, equinoxes, signs of the zodiac and ages of man. An [[Ogham inscription is in the centre. Miniature from the twelfth-century English medieval manuscript MS Oxford St John's College 17, folium 7 verso. Copy from original about 1000 AD by Byrhtferth.]] Byrhtferth (; ) was a priest and monk who lived at Ramsey Abbey in Huntingdonshire (now part of Cambridgeshire) in England. He had a deep impact on the intellectual life of later Anglo-Saxon England and wrote many computistic, hagiographic, and historical works. He was a leading man of science and best known as the author of many different works (although he may not have written many of them). His Manual (Enchiridion), a scientific textbook, is Byrhtferth's best known work.

He studied with Abbo of Fleury, who was invited to Ramsey Abbey by Oswald of Worcester to help teach. Abbo was there during the period 985 to 987, and became a large influence on Byhrtferth who was interested in the same studies, such as history, logic, astronomy, and mathematics. We do not have contemporary biographies of Byrhtferth, and the only information we have is that given in his Manual and his Preface.