This dissertation is a systematic in-depth analysis of social democracy in Turkey, with particular reference to Western Europe. The research develops a framework for the analysis of social democracy in Western Europe and Turkey in a comparative setting. Whereas the origins and development of the social democratic parties in Western Europe have been explored in the formative phase of the Industrial society in Europe, the birth and the evolution of Cumhuriyet Halk Partisi (CHP) have been scrutinised in the First Turkish Republic, as grounding to the structural conjuncture prevailing within the relevant cases. Accordingly, the analysis of the social democratic parties in these polities have been carried out on the basis of ideology, social basis of support, strategy and organisation respectively. Therefrom, the status of social democracy in Turkey is evaluated while holding the Western European case as the reference. In this context, the extent to which Turkish social democracy diverges from the homeland of social democracy has been elucidated.