State socialism, broadly speaking, is any variety of socialism which relies on ownership of the means of production by the state. State socialism is often referred to simply as "socialism"; the attributive "state" is usually added only by socialists with a different vision, wishing to criticise state socialism; for example, anarchists.

Today, many European political parties on the political left advocate varying forms of state ownership, in the form of social democracy. These moderate socialists do not advocate the overthrow of capitalism in a socialist revolution, so they also accept the continuing existence of the capitalist state and the capitalist economic system, only turned to more social purposes.

Democratic Socialists argue for a gradual, peaceful transition from capitalism to (full) socialism. They wish to abolish capitalism, but through evolution rather than revolution. (however, in modern political terminology, "democratic socialism" and "social democracy" are often used interchangeably)

In contrast, Marxism holds that a socialist revolution is the only practical way to implement fundamental changes in the capitalist system. Furthermore, it holds that after a certain period of time under socialism, the state should "wither away", producing a communist society.

Of course, the state did not, in fact, wither away in the 20th century's Communist states. Some Marxists defend them and contend that the transitional period simply wasn't finished. Other Marxists denounce those "Communist" states as Stalinist, arguing that their leadership was corrupt and that it abandoned Marxism in all but name. In particular, some Trotskyist schools of Marxism call those countries state socialist to contrast them with proper socialism; other Trotskyist schools call them state capitalist, to emphasise the lack of true socialism.

Libertarian socialists go further, deriding even Marxism as state socialism. They use the term as the primary contrast with their own form of socialism, which involves collective ownership of the means of production without state intervention.

See also: new class, state capitalism, bureaucratic collectivism, coordinatorism,degenerated workers state and deformed workers state.