Conflict between different classes in a society. The idea of class struggle held an important place in Marxism. Karl Marx divided society into two broad groups: the capitalists, or bourgeoisie, and the proletariat, or workers. Their interests were inevitably opposed, according to Marx, because one group (the proletariat) was always being exploited by the other (the bourgeoisie), so that capitalist society was a constant struggle between them. Marx believed that eventually the proletariat would triumph and a new classless society would emerge.

The idea of class struggle, as with other main tenets of Marxism, holds much less appeal worldwide now than it has done for most of this century, because of the general failure and collapse of Marxist systems around the globe.