Theognius was a monk from Cappadocia who lived during the late antique period. After entering monastic life, he relocated to the Gethsemane monastery located in Jerusalem. While serving in a leadership capacity at the monastery, he was noted for his wise administration. He eventually chose to live in seclusion near a lake by the Jordan River. He died in Palestine around the year 522 or 523 at approximately 97 years of age.