1991, at the time of the most recent census, Greece had a population of 10,259,900. In 2001 the country had an estimated population of 10,623,835. Declining birth rates have resulted in a very low rate of population increase. In 1951 the birth rate was 20.3 per 1,000 persons; by 2001 it had decreased to 9.8 per 1,000. In 2001 male life expectancy at birth was 76 years, and female life expectancy was 81 years.

The inherent instability of the Balkan Peninsula—located as it is at the crossroads of invading Turks, migrating Slavs, and colonizing powers from western or central Europe (Venetians, Austro-Hungarians)—has bequeathed a bewildering amount of cultural confusion to Greece. Even in the south or on the islands, centuries of population migration and forced population exchanges continued well into the 20th century. Despite the long Ottoman administration (perhaps because of its failure to create a nation-state), all but a very small part of the population belong to the Church of Greece (Greek Orthodox church). This body appoints its own ecclesiastical hierarchy and is headed by a synod of 12 metropolitans under the presidency of the archbishop of Athens. The Greek church has links in dogma with the other Orthodox churches. Virtually all Cretans belong to a special branch of the Church of Greece, headed by the archbishop of Crete and directly responsible to the patriarchate of Constantinople.