English monk, among the most learned and well-read scholars of the 10th and 11th centuries, who is best known for his Enchiridion, a scientific textbook.

Byrhtferth was a monk at Ramsey Abbey in England and was a student of the scholar Abbo of Fleury. Little else is known of Byrhtferth's life. Abbo spent two years (985–987) teaching at Ramsey, and this time proved to be extremely influential for Byrhtferth. His first writings (c. 988–996) involved arithmetical formulas, tables, and calculations for determining the date of Easter. These mathematical ideas were taken from Abbo's Computus and expanded upon. Influenced by the scientific works of St. Bede the Venerable (Bede the Venerable, Saint), Byrhtferth's Enchiridion (composed 1010–12; “Manual”; Eng. trans. Byrhtferth's Enchiridion) documents the basic science of the Anglo-Saxon period and is the most significant composition of its kind.

Byrhtferth wrote several historical works, including Historia regum (“History of the Kings”), which documents the earliest kingdoms in English history through the death of King Alfred. Byrhtferth also wrote accounts of the lives of several saints. He was fluent in both Latin and Old English. His works show his familiarity with a wide range of writings, including poetry and religious teachings.