The Eastern Orthodox Church and the Catholic Church were the same church until the Great Schism of about 1,000. At that time a split that had been occurring over a couple of centuries became formalized, and two separate churches were formed from the single church.
The ostensible reason was a dispute about the legitimacy of icons as an aid the worship.
The underlying reason was that, after Charlemagne's reign, Western Europe was emerging from what are called the Dark Ages to become a power that was capable of challenging the Eastern Roman Empire.
There was no single founder nor a single date of foundation. The Eastern Orthodox church and the Roman Catholic church had emerged as the "Orthodox" church for most of Europe after a series of church councils from the 4Th century onwards. At each council different churches split off from this Orthodox core such as the Arians at Nicaea (AD 325) and the Asian Orthodox Churches at Chalcedon.
This orthodox church dominated the early middle ages. It was divided into different provinces. Those in the west looked to the Bishop of Rome (known as the Pope) for spiritual guidance and court rulings while those in the east tended to look to the Patriarch of Constantinople. Yet, they still officially were the same church. However, over time, practices and beliefs in each faction began to veer further and further apart. Moreover, the Pope began to declare that he had precedence over the Patriarch. Relations got worse and worse until in 1054. In what is known as the "Great Schism" or the "East-West Schism," emissaries from the pope to the patriarch excommunicated the patriarch. The patriarch responded by excommunicating the pope. Neither side really expected the squabble to last long, but to this day, the two churches remain separated.
The Eastern Orthodox church considers itself the true orthodox church and as such founded at the very beginning by the Apostles. The Roman Catholic church thinks the same thing. I'm not going to get into which is right. But the two existed as separate entities from 1054 onwards.
Several different churches belong to the Eastern Orthodox communion. The largest (and the best known) are the Russian and the Greek Churches. Many of the churches of Eastern Europe, including those of Serbia, Georgia and Romania also belong to the communion.
Jesus, A.D. 31.
And Jesus answered him, "Blessed are you, Simon Bar-Jonah! For flesh and blood has not revealed this to you, but my Father who is in heaven. And I tell you, you are Peter, and on this rock I will build my church, and the gates of hell shall not prevail against it. Matthew 16:17-18. Note the possessive "my church"--it wasn't founded by anyone else.
There are subgroups corresponding to various regions (Jerusalem, Antioch, Greece, Romania, Russia, etc.).
Who is the founder of the eastern orthodox church?
