Isaija the Monk (c.1300 – after 1375) was a 14th-century Serbian monk, one of many Serbian monk-scribes in the Middle Ages who translated ancient Greek manuscripts into the Serbian recension of Old Church Slavonic. His major work is the translation of the works of Pseudo-Dionysius the Areopagite. At the end of his Pseudo-Dionysius the Areopagite translation, Isaija added an inscription and used a cryptogram to write his name. Isaija had an anonymous disciple, known only as Isaija's Disciple, who wrote the biography of "Isaija the Monk". No biographical data of this author is extant.