There has never before been such a concentration of wealth in so few hands, nor such record proportions of social inequality and these disparities are reflected in the impoverishment of the working class and the enrichment of an extremely small percentage of the world's population. In the 19th century unions emerged to fight against this social inequality and so became the defenders of the working class. Yet, after 150 years of such efforts, social inequality remains at an unprecedented high. This thesis seeks to explain exactly why unions were incapable of resolving this inequality, and thus why they failed to improve working class living conditions. Utilizing a historical material approach and employing a Marxist theory, this thesis explores the reasons for the unions' objective limitations. Through analyzing unions' origins, development and role in the fight for the emancipation of the working class, this thesis seeks first to present a theoretical understanding of the unions' purpose and their limitations. Second, guided by Marxist theory I detail one particular historical experience — the German union movement — and describe the movement's shift from a genuinely working class organization to an organization that fails to represent its constituents' interests. Lastly, I argue that the German case exemplifies a broader historical trend: union failure is not simply a European issue but an international one. In doing so, I argue that the unions' inherent nature and changing socio-economic environment engenders their failure, since the unions' work remains entrenched within the boundaries established by the capitalist system and their emergence in the framework of the national state and economy led to their complete deterioration in today's globalized system.