Central and Eastern Europe is a term describing former communist states in Europe, after the collapse of the Iron Curtain in 1989/90. In scholarly literature the abbreviations CEE or CEEC are often used for this concept. CEE includes all the Eastern bloc countries west of the post-World War II border with the former Soviet Union, the independent states in former Yugoslavia (which were not considered part of the Eastern bloc), and the three Baltic states — Estonia, Latvia, Lithuania — that chose not to join the CIS with the other 12 former republics of the USSR. The transition countries in Europe and Central Asia are thus classified today into two political-economic entities: CEE and CIS. The CEE countries are further subdivided by their accession status to the European Union (EU): the eight first-wave accession countries that joined the EU in May 2004 (Estonia, Latvia, Lithuania, Poland, Czech Republic, Slovakia, Hungary, and Slovenia) and the two second-wave accession countries that joined in January 2007 (Romania and Bulgaria). According to the World Bank, "the transition is over" for the 10 countries that joined the EU in 2004 and 2007.

Eastern Europe is the eastern part of Europe. The term has widely disparate geopolitical, geographical, cultural and socioeconomic readings, which makes it highly context-dependent and even volatile, and there are "almost as many definitions of Eastern Europe as there are scholars of the region". A related United Nations paper adds that "every assessment of spatial identities is essentially a social and cultural construct".

One definition describes Eastern Europe as a cultural (and econo-cultural) entity: the region lying in Europe with main characteristics consisting in Byzantine, Orthodox and minor and limited Ottoman influences.

Another definition, considered outdated by several authors, was created during the Cold War and used more or less synonymously with the term Eastern Bloc. A similar definition names the formerly communist European states outside the Soviet Union as Eastern Europe.

Eastern Europe, home of the bulk of world Jewry until the 1940s, is the birthplace of Hasidic Judaism, Litvak Judaism and several Orthodox churches.