Global Eastern Orthodox Population: 200–300 Million

The Eastern Orthodox Church (officially the Orthodox Catholic Church) has approximately 200–300 million adherents worldwide, making it the second-largest Christian communion after the Roman Catholic Church (~1.3 billion).

Geographic Distribution

• Russia: ~100–110M (Russian Orthodox Church)
• Romania: ~16M
• Greece: ~9M
• Serbia: ~6–7M
• Bulgaria: ~4–5M
• Ukraine: ~15–30M (split between OCU and UOC-MP; war complicates data)
• Belarus, Moldova, Georgia, Cyprus, North Macedonia, Montenegro: Majority Orthodox
• Diaspora: USA (~1–2M), Canada, Western Europe, Australia, Africa, Latin America

Structure

Autocephalous (self-governing) churches in full communion—no single pope. The Ecumenical Patriarch of Constantinople (Istanbul) holds "first among equals" honorific primacy.

Data Challenges

• Census vs. baptismal vs. self-ID numbers differ
• Political boundaries, migration, secularization affect counts
• "Adherents" may include cultural/nominal affiliates