John of Manglisi was a Georgian hierarch and missionary who was spiritually formed in the David-Gareja wilderness before serving as bishop of Manglisi. Born in 1668, he is associated with the Saakadze family and was, according to the synaxarion, distinguished in ascetic virtue; he was ordained a hieromonk and subsequently consecrated bishop. He is commemorated on March 28.
After his episcopal service, John devoted himself to missionary labor among populations to the north and east of Georgia, in regions bordering the Caspian Sea. The tradition records that in 1724 he departed for Derbend in Dagestan, where he built a wooden church and began preaching Christianity among the local people. His mission unfolded amid the difficult political circumstances of the period, and he is said to have worked with the support of King Vakhtang VI of Kartli and of the Russian tsar Peter the Great.
According to the accounts of his life, John reposed in 1751 at Kizliar, and his relics were afterward translated to Tbilisi and interred in the Sioni Cathedral. He is venerated in the Georgian Orthodox tradition as a bishop and ascetic who carried Christian preaching into frontier regions during the early modern period.