Sergius of Radonezh
Cyril of Beloozero (Cyril of Beloezero, - "Kirill Belo(e)zersky"; 1337 – 1427) was a monk and saint of the Russian Orthodox Church who lived in the 15th century. Saint Cyril was a disciple of Saint Sergius of Radonezh. In 1397, he founded the Kirillo-Belozersky Monastery in Northern Russia, in the present-day Vologda Oblast.