विकासशील देश शब्द का प्रयोग किसी ऐसे देश के लिए किया जाता है जिसके भौतिक सुखों का स्तर निम्न होता है । चूंकि विकसित देश नामक शब्द की कोई भी एक परिभाषा अंतरराष्ट्रीय स्तर पर मान्यता प्राप्त नहीं है, अतः विकास के स्तर इन तथाकथित विकासशील देशों में व्यापक रूप से भिन्न हो सकते हैं। कुछ विकासशील देशों में, औसत रहन-सहन का मानक भी उच्च होता है।

A developing country is a sovereign state with a less developed industrial base and a lower Human Development Index (HDI) relative to other countries. However, this definition is not universally agreed upon. There is also no clear agreement on which countries fit this category. The terms low and middle-income country (LMIC) and newly emerging economy (NEE) are often used interchangeably but refers only to the economy of the countries. The World Bank classifies the world's economies into four groups, based on gross national income per capita: high, upper-middle, lower-middle, and low income countries. Least developed countries, landlocked developing countries and small island developing states are all sub-groupings of developing countries. Countries on the other end of the spectrum are usually referred to as high-income countries or developed countries.