RESUMEN: Se pretende establecer el contenido del concepto "marxismo•• con base en la historia secular del fenómeno conocido con ese nombre. Para ello, se avanzan cinco tesis sobre su contenido teórico, su relación con Marx, su origen y fundación en el pensamiento de Engels y se precisa su relación y distinción con los conceptos de socialismo y de comunismo.ABSTRACT: An attempt is made at determining the contents of the concept of "marxism," based on the already secular history of the phenomenon known under such a name. This is achieved by means of five theses on its theoretical contents, its relationship to Marx, its origin and foundation in Engels' thought; the relationship to and distinction from the concepts of socialism and communism is specified.