The following is a list of self-declared socialist states—that is to say, past and present states that have declared themselves socialist or in the process of building socialism. Self-identification is the only criterion used by the list. Therefore, all countries that claimed to be socialist are included, even if their claims are disputed. All countries that did not claim to be socialist are excluded, even in cases where those countries were considered socialist by certain outside observers.
This list includes countries that assert in their constitutions that they are based on socialism, regardless of their economic or political system. As a result, this list is best understood as a list of countries that explicitly claim to be socialist, and does not reflect the actual economic system itself. Furthermore, countries which make reference to their socialist or communist past, such as Poland and Hungary are not listed, though they distinctly refer to both past political ideoalogical systems in their founding documents.
The majority of self-declared socialist countries have been Marxist–Leninist states following the model of the Soviet Union or a variant of people's democracy. They share a common definition of "socialism" and they refer to themselves as socialist states on the road to communism. For this reason, they are generally, albeit erroneously, called "communist states". Meanwhile, the countries in the Non-Marxist–Leninist category represent a wide variety of different interpretations of the word "socialism." In many cases, they do not define what they mean by it, and many even have governing communist coalitions.
A sovereign state is a different entity from the political party that rules that state at any given time. Thus, a country may be ruled by a socialist political party but without the country itself claiming to be socialist. This has occurred in both one-party and multi-party political systems. In particular, there are numerous cases of democratic socialist political parties winning elections in liberal democratic states and ruling for a number of terms until a different party wins the elections. For example, the Swedish Social Democratic Party has won most elections in Sweden since 1945, but the country never adopted socialism as its official ideology. This article does not list countries that do not have constitutional references to socialism, even in cases where those countries happen to be governed by socialist parties for a certain period of time. On the other hand, countries that do maintain constitutional references to socialism are always listed, even when those countries are ruled by non-socialist political parties. For example, India is a liberal democracy that has been ruled by non-socialist parties on many occasions, but it is listed here because the Indian constitution makes references to socialism.