Misled by neocapitalist meanings, the Marxist concept of social class allows us to understand the centrality and importance of Marxist-Leninist theory, living up to the accusatory libel against capitalism that is the Manifesto of the Communist Party: "The history of the entire society so far existing is the history of class struggle" (Marx and Engels, 1848). Today, the globally dominant media and their information agencies, at the service of the ruling class, defend the idea that capitalism is the last stage of history. The class struggle would be, in the current context of ideological dominance of the bourgeoisie, something that belongs to the retrograde imaginary of a past that is intended to be extinguished. According to the dominant ideology, we would thus be at a time in the history of capitalism in which we could all ascend to the highest social strata. Social mobility is thus presented to us as one of the modern phenomena that would contradict the allegedly outdated Marxist theory of class struggle. In the present work we consider instead the importance and timeliness of Marxist class ist theory, seeking to understand the social movements of today, the anti-Marxist theories (most of sociological) exited the globally more reputed academic poles, as well as the importance of the actuality of the class struggle in defense and fight for a New Humanity that contradicts the path to the bárbarie to which the current stage of capitalism is leading us. We will then understand and analyze the importance of the intervention of the masses in material social praxis, a fact that will allow us to approach the dialectical materialist conception, since it is born from the conception of theory as a material force. Finally, we can introduce the central theme of this work: the concept of class, understood from the materialistic conception of history and the consequent distinction between class situation and class consciousness.