Social democracy emerged in the late nineteenth century and has become a leading political ideology in Europe. This short history approaches the evolution of this ideology as a body of political thought and political practices. It expounds the development, transformation and practice of European social democracy through the analysis of four key moments in its history: its origins and rise as a key political force in European politics, the second revisionist phase with the embrace of capitalism in the postwar period, the Third Way of the 1990s and the contemporary crisis of social democracy in an era of fragmented politics. The book offers a fresh and engaging discussion of one of the most enduring ideologies of the European political sphere and its manifestations in different countries of the region.