The Apostolic Autocephalous Orthodox Church of Georgia (Georgian: საქართველოს სამოციქულო ავტოკეფალური მართლმადიდებელი ეკლესია, romanized: sakartvelos samotsikulo avt'ok'epaluri martlmadidebeli ek'lesia), commonly known as the Georgian Orthodox Church or the Orthodox Church of Georgia, is an autocephalous Eastern Orthodox church in full communion with the other churches of Eastern Orthodoxy. It is Georgia's dominant religious institution, and a majority of Georgian people are members. The Orthodox Church of Georgia is one of the oldest churches in the world. It asserts apostolic foundation, and that its historical roots can be traced to the early and late Christianization of Iberia and Colchis by Andrew the Apostle in the 1st century AD and by Saint Nino in the 4th century AD, respectively. As in similar autocephalous Eastern Orthodox Christian churches, the church's highest governing body is the holy synod of bishops. The church is headed by the Patriarch of All Georgia, Ilia II, who was elected in 1977.

Eastern Orthodox Christianity was the state religion throughout most of Georgia's history until 1921, when the country, having declared independence from Russia in 1918, was occupied by the Red Army during the Soviet invasion of Georgia, becoming part of the Soviet Union. The current Constitution of Georgia recognizes the special role of the Georgian Orthodox Church in the country's history, but also stipulates the independence of the church from the state. Government relations are further defined and regulated by the Concordat of 2002.

The Georgian Orthodox Church is the most trusted institution in Georgia. According to a 2013 survey, 95% respondents had a favorable opinion of its work. It is highly influential in the public sphere and is considered Georgia's most influential institution.

According to Georgian Orthodox Church tradition, the first preacher of the Gospel in Colchis and Iberia (modern-day Western and Eastern Georgia) was the apostle Andrew, the First-called. According to the official church account, Andrew preached across Georgia, carrying with him an acheiropoieta of the Virgin Mary (an icon believed to be created "not by human hand"), and founded Christian communities believed to be the direct ancestors of the church. However, modern historiography considers this account mythical, and the fruit of a late tradition, derived from 9th-century Byzantine legends about the travels of St. Andrew in eastern Christendom. Similar traditions regarding Saint Andrew exist in Ukraine, Cyprus and Romania. Other apostles claimed by the church to have preached in Georgia include Simon the Canaanite (better known in the West as Simon the Zealot), said to have been buried near Sokhumi, in the village of Anakopia, and Saint Matthias, said to have preached in the southwest of Georgia, and to have been buried in Gonio, a village not far from Batumi. The church also claims the presence in Georgia of the Apostles Bartholomew and Thaddeus, coming north from Armenia.

The propagation of Christianity in present-day Georgia before the 4th century is still poorly known. The first documented event in this process is the preaching of Saint Nino and its consequences, although exact dates are still debated. Saint Nino, honored as Equal to the Apostles, was according to tradition the daughter of a Roman general from Cappadocia. She preached in the Caucasian Kingdom of Iberia (also known as Kartli) in the first half of the 4th century, and her intercession eventually led to the conversion of King Mirian III, his wife Queen (later Saint) Nana and their family. Cyril Toumanoff dates the conversion of Mirian to 334, his official baptism and subsequent adoption of Christianity as the official religion of Iberia to 337. From the first centuries C.E., the cult of Mithras, pagan beliefs, and Zoroastrianism were commonly practiced in Georgia. However, they now started to gradually decline, even despite Zoroastrianism becoming a second established religion of Iberia after the Peace of Acilisene in 378, and more precisely by the mid-fifth century.

The royal baptism and organization of the church were accomplished by priests sent from Constantinople by Constantine the Great. Conversion of the people of Iberia proceeded quickly in the plains, but pagan beliefs long subsisted in mountain regions. The western Kingdom of Lazica was politically and culturally distinct from Iberia at that time, and culturally more integrated into the Roman Empire; some of its cities already had bishops by the time of the First Council of Nicea (325).

The conversion of Iberia marked only the beginnings of the formation of the Georgian Orthodox Church. In the following centuries, different processes took place that shaped the church, and gave it, by the beginning of the 11th century, the main characteristics that it has retained until now. Those processes concern the institutional status of the church inside Eastern Christianity, its evolution into a national church with authority over all of Georgia, and the dogmatic evolution of the church.

In the 4th and 5th centuries, the Church of Iberia was strictly subordinated to the Apostolic See of Antioch: all of her bishops were consecrated in Antioch before being sent to Iberia. Around 480, "[i]n an attempt to secure K'art'velian support and to acknowledge local support of the empire, the Byzantine government recognized – and perhaps itself instigated – the change in status of the K'art'velian chief prelate from archbishop to catholicos".