Karl Marx is the sociologist most famously associated with the concept of "class struggle." Marx believed that history is shaped by the struggles between different classes, particularly between the proletariat (working class) and the bourgeoisie (capitalist class). This struggle, he argued, would eventually lead to the overthrow of capitalism and the establishment of a classless society.
Max Weber, Émile Durkheim, and George Herbert Mead made significant contributions to sociology, but the concept of class struggle is most closely associated with Marx.