The book is dedicated to forgotten dramatic pages in the history of the 18th century, associated with the appearance of impostors accepted by the people under the name of the Russian Emperor Peter III, not only in Russia (the most famous of them is E. I. Pugachev), but also beyond its borders (Stepan Maly in Montenegro, “Russian prince” in the Czech Republic, etc.). Considering the events of the 60-70s of the 18th century associated with the appearance of impostors, in the context of inter-Slavic contacts, the author dwells on the reasons for the emergence of posthumous legends around the name of Peter III and his personality. The monograph is based on materials from the author’s previous book, “The Legend of the Russian Prince” (L.: Nauka, 1987), expanded and supplemented with new data obtained in the archives of the USSR and Germany, from publications of domestic and foreign research. For historians and the general public readers interested in the history of Russia and Slavic countries.