The term "Third World" arose during the Cold War to define countries that remained non-aligned with either NATO or the Warsaw Pact. The United States, Canada and their allies represented the "First World", while the Soviet Union, China, Cuba, North Korea, Vietnam, and their allies represented the "Second World". This terminology provided a way of broadly categorizing the nations of the Earth into three groups based on political divisions. Due to the complex history of evolving meanings and contexts, there is no clear or agreed-upon definition of the Third World. Strictly speaking, "Third World" was a political, rather than economic, grouping.

तृतीय विश्व या तीसरी दुनिया की संकल्पना शीत युद्ध के समय में आयी। उन देशों के समूह को 'तृतीय विश्व' कहा गया जो न तो नाटो के साथ थे न ही सोवियत गुट के साथ। संयुक्त राज्य अमेरिका, पश्चिमी यूरोप के देश तथा उनके साथी देशों को 'प्रथम विश्व' कहते थे; सोवियत संघ, चीन, क्यूबा तथा उनके सहयोगियों को 'द्वितीय विश्व' कहते थे।