Archbishop Flavian (Theophylact Theophylactovich Slesarev; March 1, 1879 –December 25, 1960) was born to peasants in the village Gorodishche, in the Don Host oblast.
On September 22, 1905, he was ordained as deacon of the Church of the Dormition in the village Gorodishche. On February 12, 1910, he was ordained as priest of the same church. Both ordinations were conducted by archbishop John. Father Theophylact participated in the congresses of the Donetsk-Don diocese and the Holy Councils in Moscow. He was elected the rural dean of the 5 diocesan deanery.
In 1937, he was promoted to the rank of protopriest by bishop Vikentiy and on May 27, 1947, he was elected as an episcopal candidate for the newly formed Donetsk-Don and Caucasian diocese.
On March 17, 1948, father Theophylact accepted monasticism and on March 22, he was ordained as bishop of the Rostov cathedra by archbishop Irinarkh (Parfenov) in cooperation with bishop Gerontius (Lakomkin) of Yaroslavl-Kostroma.
On June 12, 1951, after the death of bishop Gerontius, he was elected as proxy Archbishop. On March 12, 1952, after the death of archbishop Irinarkh, bishop Flavian was elected to the Moscow Primacy by a council of bishops, clergy and laity. The enthronement of archbishop Flavian was conducted by bishop Joseph (Morzhakov) on March 16, 1952.
Archbishop Flavian died on December 25, 1960.