Social democracy has had a significant impact on the shaping of modern Western society and remains one of the leading political forces in the countries of the European Union. In Russia, however, the fate of social democracy was completely different - after 1917 it was completely defeated, and attempts to recreate it in the late XX - early XXI centuries were unsuccessful. The present book explores the historical paths of European and Russian social democracy. Its first part is devoted to more than a century of ideological and political evolution of Western social democracy - from K. Marx, K. Kautsky and E. Bernstein to T. Blair and G. Schroeder. The authors examine in detail the formation of the Socialist International, the crisis of the social democratic movement in the last quarter of the twentieth century and the formation of a "new" social democracy. The second part of the book is devoted to the difficult historical path of Russian Social Democracy (Menshevik and modern) and its prospects. For political scientists, historians, teachers of social sciences and their students, graduate students, politicians, civil servants, and all those interested in the political history of the West and Russia.