The Demographics of Greece refer to the demography of the population that inhabits the Greek peninsula. The population of Greece was calculated as 10,815,197 in the 2011 census.

Greece was inhabited as early as the Paleolithic period. Prior to the 2nd millennium BC, the Greek peninsula was inhabited by various pre-Hellenic peoples, the most notable of which were the Pelasgians. The Greek language ultimately dominated the peninsula and Greece's mosaic of small city-states became culturally similar. The population estimates on the Greeks during the 4th century BC, is approximately 3.5 million on the Greek peninsula and 4 to 6.5 million in the rest of the entireMediterranean Basin,[6] including all colonies such as those in Magna Graecia, Asia Minor and the shores of the Black Sea.
During the history of the Byzantine Empire, the Greek peninsula was occasionally invaded by the foreign peoples like Goths,Avars, Slavs, Normans, Franks and other Romance-speaking peoples who had betrayed the Crusades. The only group, however, that planned to establish permanent settlements in the region were the Slavs. They settled in isolated valleys of thePeloponnese and Thessaly, establishing segregated communities that were referred by the Byzantines as Sclaveni. Traces of Slavic culture in Greece are very rare and by the 9th century, the Sclaveni in Greece were largely assimilated. However, some Slavic communities managed to survive in rural Macedonia. At the same time a large Sephardi Jewish emigrant community from the Iberian peninsula established itself in Thessaloniki, while there were population movements of Arvanites and Vlachs, who established communities in several parts of the Greek peninsula. The Byzantine Empire ultimately fell to Ottoman Turks in the 15th century and as a result Ottoman colonies were established in the Balkans, notably in Macedonia, the Peloponnese andCrete. Many Greeks either fled to other European nations or to geographically isolated areas (i.e. mountains and heavily forested territories) in