Eastern Orthodoxy constitutes the second largest Christian denomination in Europe. Eastern Orthodox Christians are predominantly present in Eastern and Southeastern Europe, and they are also significantly represented in diaspora throughout the Continent. The term "Eastern Orthodox Europe" is informally used to describe the predominantly Eastern Orthodox countries of Bosnia, Belarus, Bulgaria, Cyprus, Georgia, Greece, Moldova, Montenegro, North Macedonia, Romania, Russia, Serbia and Ukraine.
The term Byzantine commonwealth was coined by 20th-century historian Dimitri Obolensky to refer to the area where Byzantine general influence (Byzantine liturgical and cultural tradition) was spread during the Middle Ages by the Byzantine Empire and its missionaries. This area covers approximately the modern-day countries of Greece, Cyprus, North Macedonia, Bulgaria, Serbia, Montenegro, Romania, Moldova, Ukraine, Belarus, southwestern Russia, and Georgia (known as the region of Eastern Orthodoxy in Europe or the Orthodox Civilization). According to Anthony Kaldellis, the Byzantines in general did not have a ecumenical outlook, nor did they think about the notion of a panorthodox commonwealth, which he describes as "Roman chauvinism".