Book of Doctor of Historical Sciences B.M. Kloss presents the first monographic study on the origin and existence of the term "Russia" in Russian writing of the XIV-XVIII centuries. (from the first mention to the official name of the state). The origin of the name "Russia" is closely related to Greek culture. The main problem was to establish the time of penetration of the name "Russia" into medieval Russian writing, to explain the reason for replacing the ancient name "Rus" with "Russia," its connection with certain public circles and approval in the state title. A special subject of research is such variants of the name as "Great Russia," "Russians," dialectisms like "Rasea," the reasons for the transformation of the original name "Russia" (with one "c" - in accordance with the Greek original) into the name "Russia" (with two "c"). The work is based on the study of numerous manuscript and printed sources, many of which are first introduced into scientific circulation.