Abstract: The rise of nationalism in the 20th century is a manifestation of struggles for national liberation and self-determination in countries and regions of the Third World dominated by colonialism and imperialism. Today, with the internalization of capital and imperialist domination across the globe, nationalism has become a worldwide phenomenon, spreading to every corner of the world. This study examines the nature and development of nationalism and national movements and provides an analysis of the class basis of these phenomena within the framework of the relationship between class, nation and state-an analysis that situates nationalism and national movements within the context of class relations and class struggles. After an overview of the emergence of nationalism and national movements in the 20th century, we provide a general discussion on the class nature of nationalism and conclude with case studies of contemporary national movements focusing on their class nature. We argue that the class nature of the society being built in the aftermath of a national struggle is very much a reflection of the class nature of the national movement in question and that a class analysis approach to the phenomenon of the nationalism can provide us a better understanding of the nature of class struggle and social transformations in post-liberation societies in the Third World.