The Kastamonitou Monastery is located in the interior of the peninsula of Mount Athos, between the monasteries of Docheiariou and Zographou. Virtually no documents survive from the Byzantine period, so little is known of its history. Dedicated to St. Stephen, Kastamonitou was founded in the mid-11th century, probably by a native of Kastamon in Paphlagonia or a member of the Kastamonites family. Until the 14th century it was a modest establishment, inhabited by Greek monks. After a fire in the 1420s, Kastamonitou was restored through the generosity of the Serbian general Radit, attracted numerous slavophone monks, and remained prosperous until around 1500. The present monastery is of modern (18th or 19th century) construction. The library contains 40 manuscripts of Byzantine date. The dates of three supposedly Byzaninte wonder-working icons in the monastery's church have not yet been established.
Oxford Dictionary of Byzantium