This article is devoted to the scholarly work of the prominent Russian historian Igor Iakovlevich Froianov who died last December. He is a brilliant representative of the Petersburg Historical School, and first and foremost — a well-known specialist in the history of so called Kievan Rus. He created a complex concept of the “obcshinno-vechevaia” civilization of Old Rus. His concept is ultimately comprehensive because he studied in consecutive order practically all sides of such a phenomenon as Kievan Rus: economy, political life, social struggle, culture. His concept emerged in confrontation with the prevalent Soviet vision of this history, and at the same time from the very beginning it became a creative continuation and development of pre-revolution historiography. He also devoted several interesting and important works to the period of Moscow Rus, particularly to the process of formation of the Russian monarchy. These works made an excellent foundation for the new original view of this epoch of the Russian history, different from other concepts. Froianov’s legacy is divided into two parts: before and after the middle of the 1990s when so called “perestroika” took place in the USSR. On the one hand, he continued to study the old time. On the other hand, a number of his later works are devoted to the history of Russian revolution (1917) and to the above-mentioned “perestroika”. These works are closely connected with a publicistic genre which captivated him in those years. However, it is to a certain extent a continuation of his previous interests as these works are dedicated to the same Russian-Orthodox Civilization.