The U.S. government estimates the total population at 10.6 million (midyear 2020 estimate). According to research polls, 81 to 90 percent of the population identifies as Greek Orthodox, 4 to 15 percent atheist, and 2 percent Muslim.

Approximately 140,000 Muslims live in Thrace, according to government sources using 2011 data; they are largely descendants of the officially recognized Muslim minority according to the 1923 Treaty of Lausanne. According to a Pew Research Center study released in November 2017, an additional 520,000 Muslims – mostly asylum seekers, refugees, and other migrants from Southeastern Europe, South and Southeast Asia, the Middle East, and North Africa – reside throughout the country, clustered in communities by their countries of origin or in reception facilities. Government sources estimate half reside in Athens.

Members of other religious communities that together constitute less than 5 percent of the population include Old Calendarist Orthodox, Catholics, Protestants, Jehovah’s Witnesses, Jews, members of polytheistic Hellenic religions, Scientologists, Baha’is, members of The Church of Jesus Christ of Latter-day Saints, Sikhs, Seventh-day Adventists, Buddhists, and members of the International Society of Krishna Consciousness (ISKCON). Independent and media sources estimate Ethiopian Orthodox number 2,500, and Assyrians less than 1,000. According to the Armenian Orthodox Archbishop, interviewed in 2018, approximately 100,000 Armenian Orthodox live in the country.