A Third World country is a term used to describe countries that were not aligned with either the capitalist First World or the communist Second World during the Cold War. The term was used to classify countries that did not pick a faction during the Cold War. Countries that aligned with NATO were considered part of the “First World,” while countries that aligned with the Warsaw Pact were part of the “Second World” . The Third World was normally seen to include many countries with colonial pasts in Africa, Latin America, Oceania, and Asia. Nonetheless, some countries that were historically referred to as “Third World” include Afghanistan, Angola, Argentina, Bangladesh, Bolivia, Burkina Faso, Cambodia, Chad, China, Congo, the Dominican Republic, Ecuador, Egypt, El Salvador, Ethiopia, Ghana, Guatemala, Haiti, Honduras, India, Indonesia, Iraq, Jamaica, Kenya, Laos, Lebanon, Madagascar, Malawi, Mali, Morocco, Mozambique, Nepal, Nicaragua, Niger, Nigeria, Pakistan, Rwanda, Senegal, Somalia, Sri Lanka, Sudan, Tanzania, Uganda, Vietnam, and others.

Today, the term "Third World" has decreased in use and is being replaced with terms such as developing countries, least developed countries, or the Global South. The modern definition of “Third World” is used to classify countries that are poor or developing. Countries that are part of the “third world” are generally characterized by high rates of poverty, economic and/or political instability, and high mortality rates. The least developed countries (LDCs) are a group of countries that have been identified by the UN as "least developed" based on three criteria: low-income estimate of the gross national income (GNI) per capita, weak human assets, and high degree of economic vulnerability.

It is important to note that the term “Third World countries” is a controversial term because it is often used to categorize nations based on their economic, social, and political status. While there is no single definition of what constitutes a third world country, the term is generally used to describe nations that are struggling to catch up with the more prosperous and developed nations of the world.