Gregory, Samblak a Russian prelate, was a native of Bulgaria, and became metropolitan of Kiev in 1414. He went to the Council of Constance in 1418, and died the year following. It is certain that this prelate was a Catholic, for his name is found in one of the ancient liturgies. The library of the synod of Moscow is in possession of twenty-seven Discourses of this metropolitan. See Hoefer, Nouv. Biog. Generale, s.v.