This article explores the anti-ecumenical movement in Russian Orthodoxy, its facets of religious separation and isolationism. The article analyzes the sociocultural and political premises on which the isolationist ideology of Orthodox fundamentalists relies, in particular defensiveness and security, both of which intertwine with revanchism, geopolitical resentment, and an idealization of the Soviet past. It also explores the cultural phenomenon of “mobilization consciousness” — a psychological conviction that positive transformation processes in Russia can only occur in circumstances of extreme stress and danger. The article also compares of key features of modern Orthodox fundamentalists and radical right movements.