Christianity has been the predominant religious influence in the territory comprising present-day Georgia since at least the fourth century A.D., when Nino of Cappadocia, the daughter of a Roman general, is said to have preached in Kartli (present-day eastern and southern Georgia; also known as Iberia) and to have been responsible for the conversion of the king and queen and their family. Christianity in Kartli was initially organized under the jurisdiction of the Church of Antioch, but in the late 5th century, a catholicos (chief bishop) was appointed for the city of Mtskheta, giving the church in the kingdom a degree of local autonomy. A united Georgian kingdom—comprising both Kartli and Colchis (present-day western Georgia)—had taken shape by 1008 under Bagrat III. In 1010, the church in the unified Kingdom of Georgia became autocephalous (self-governing), and its catholicos (Melchizedek I) was elevated to the rank of patriarch and obtained the official title of Catholicos-Patriarch of All Georgia.
From the 13th through the 18th centuries, Georgia was invaded numerous times by Mongols, Ottomans (Turks), and Safavids (Persians), and the Kingdom of Georgia became fragmented by the end of the 15th century. A notable Christian martyr of this period was Ketevan of Mukhrani, a queen who was tortured to death in 1624 after refusing demands by the Safavid ruler (Abbas I) to renounce Christianity and convert to Islam.
In 1801, the kingdoms of present-day eastern and central Georgia were occupied and annexed by the Russian Empire. The Russian authorities abolished the independent status of the Georgian church and made the region subject to the Russian Orthodox Church; the use of the Georgian language in the liturgy was suppressed, and many church buildings in Georgia were defaced and fell into disrepair. The Georgian Orthodox Church (GOC) reasserted its autocephaly after the overthrow of Tsar Nicholas II in 1917, but the Georgian church was subjected to renewed harassment in the 1920s and 1930s by the newly created Soviet Union, during the rule of the Georgian-born Soviet leader, Joseph Stalin.
As part of Stalin's efforts to unite the Soviet citizenry against the Nazi threat during World War II, state-sponsored persecution of religion was somewhat eased, and the GOC's independence from the Russian church was once again formally recognized in 1943. Restrictions on religious organizations returned after the end of the war, and the general corruption which plagued the leadership of the Georgian SSR in the early 1970s affected church officials in Georgia. When Ilia II became patriarch of the GOC in 1977, he moved to rejuvenate the church, directing the renovation of derelict churches, as well as construction of new churches. The GOC joined the World Council of Churches (WCC) in 1962, and Ilia II served as president of the WCC between 1979 and 1983.
The GOC's power and prestige in Georgian society increased significantly after Ilia II's installation as patriarch in 1977. In 1990, the Ecumenical Patriarchate of Constantinople (the "first among equals" of the Eastern Orthodox prelates) formally recognized the autocephaly of the GOC and affirmed Ilia II's title of Catholicos-Patriarch of All Georgia.