Byzantine monk who founded communal monasticism in the hallowed region of Mt. Athos (Athos, Mount), a traditional habitat for contemplative monks and hermits.

Originally named Abraham, he took the monastic name of Athanasius when he retired to Mt. Athos after forsaking the sophisticated, urban monastic life in Constantinople; there he had served as spiritual director to the general Nicephorus Phocas, later the emperor Nicephorus II Phocas.

In 963, with imperial support, Athanasius organized the scattered solitaries on Mt. Athos into the Great Laura (Greek laura, “monastery”). There, he introduced a Typicon, or rule, for cenobites (monks in community life) based on similar codes by the 4th-century monastic founder Basil of Caesarea and the 9th-century reformer Theodore Studites.

Various ecclesiastical and political factions opposed this monastic innovation and forced Athanasius to flee to Cyprus after the death of Nicephorus in 969. He returned to Mt. Athos, however, in response to a command he claimed to have received in a vision. Formal acceptance and financial assistance came from Nicephorus' successor, the emperor John I Tzimisces, who in 971–972 had settled the controversy by granting Athos its first charter. Athanasius died in the collapse of a building he was about to dedicate. His writings include a supplementary rule for monks (Hypotyposis), incorporating elements of Greek and Syriac monasticism; a detailed annotation (Diatyposis) of provisions for monastic transfer of authority; and a liturgical directory particularly for the Easter season.