Saint Leontius of Monemvasia or Saint Leontius of Achaia (Greek: Άγιος Λεόντιος o Μονεμβασιώτης ή Ὅσιος Λεόντιος ὁ ἐν Ἀχαΐᾳ), was an Eastern Orthodox Saint who was born in Monemvasia and lived in asceticism in the region of north Peloponnese in the 15th century.Details about his life are known to us mainly from his first biographer who according to some scholars is the Byzantine philosopher and Ecumenical Patriarch of Constantinople, Gennadius Scholarius. The biography entitled in Greek "Ἐγκώμιον τοῦ ὁσίου Λεοντίου τοῦ ἐν Ἀχαΐᾳ, οὗ ἡ μνήμη τελεῖται τῇ ια´ τοῦ Δεκεμβρίου μηνός" is found in the manuscript Gr. II, 186 (=1180) of the Biblioteca Marciana.