Anton Vladimirovich Kartashev (1875-1960) is a famous Russian church historian and theologian. The scientist’s works are in a strictly Orthodox spirit, fascinating and lively written. One of the most significant works of the historian was the monograph “Ecumenical Councils”, created by the author over many years. The book is dedicated to the history of the Ecumenical Councils, starting with the famous Council of Nicaea (325), which adopted the common Christian Creed, and ending with the Parisian Council (825), one of the most interesting pages in the history of Christianity. This publication is intended not only for a narrow circle of specialists, but and for everyone who today shows a keen interest in the history of religion and the Church.