Eastern Europe is a subregion of the European continent. As a largely ambiguous term, it has a wide range of geopolitical, geographical, ethnic, cultural, and socio-economic connotations. Its eastern boundary is marked by the Ural Mountains, whilst its western boundary is defined in various ways. Most definitions include the countries of Belarus, Russia, Ukraine, Moldova, and Romania while less restrictive definitions may also include some or all of the Balkans, the Baltic states, the Caucasus, and the Visegrád group.

The region represents a significant part of European culture; the main socio-cultural characteristics of Eastern Europe have historically been defined by the traditions of the East Slavs and Greeks, as well as by the influence of Eastern Christianity as it developed through the Eastern Roman Empire and the Ottoman Empire. Another definition was created by the Cold War, as Europe was ideologically divided by the Iron Curtain, with "Eastern Europe" being synonymous with communist states constituting the Eastern Bloc under the influence of the Soviet Union.

The term is sometimes considered to be pejorative, through stereotypes about Eastern Europe being inferior (poorer, less developed) to Western Europe; the term Central and Eastern Europe is sometimes used for a more neutral grouping.