Karl Marx is undoubtedly one of the most influential German philosophers and theorists in history, spanning fields such as economics, anthropology, and more. His relevance remains unbroken, especially in times of financial crisis. After an overview of his biography, this handbook presents Marx's works along with their main theses. A comprehensive chapter on concepts and contexts critically highlights the relevance of Marxian thought for contemporary theoretical discussions. For example, his diagnoses of reification and alienation, the world of work and forms of labor (such as assembly line work), the management of natural resources (sustainability), social justice (the new precariat), global economy and imperialism (globalization), as well as the paradoxes of the financial market economy are foundational to current debates. The concluding section traces the reception of Marx across various disciplines.