The Greek Orthodox Patriarchate of Antioch (Greek: Ελληνορθόδοξο Πατριαρχείο Αντιοχείας), also known as the Antiochian Orthodox Church and legally as the Rūm Orthodox Patriarchate of Antioch and All the East (Arabic: بطريركيّة أنطاكية وسائر المشرق للروم الأرثوذكس, romanized: Baṭriyarkiyyat ʾAnṭākiya wa-Sāʾir al-Mašriq li-r-Rūm al-ʾUrṯūḏuks, lit. 'Patriarchate of Antioch and All the East for the Orthodox Rum'), is an autocephalous Greek Orthodox church within the wider communion of Eastern Orthodox Christianity that originates from the historical Church of Antioch. Headed by the Greek Orthodox patriarch of Antioch, it considers itself the successor to the Christian community founded in Antioch by the Apostles Peter and Paul. It is one of the largest Christian denominations of the Middle East, alongside the Copts of Egypt and the Maronites of Lebanon.

Its adherents, known as Antiochian Christians, are a Middle-Eastern semi-ethnoreligious Eastern Christian group residing in the Levant region, including the Hatay Province of Turkey. Many of their descendants now live in the global Eastern Christian diaspora. The number of Antiochian Greek Christians is estimated to be approximately 4.3 million.

The seat of the patriarchate was formerly Antioch, in what is now Turkey. The Church of Cassian was the cathedral church of Antioch to the Melkite and Latin patriarch during late antiquity and the Middle Ages. However, in the 14th century, it was moved to Damascus, modern-day Syria. Its traditional territory includes Syria, Lebanon, Iraq, Kuwait, the Arab countries of the Persian Gulf, and also parts of Turkey. Its territory formerly included the Church of Cyprus until the latter became autocephalous in 431. Both the Orthodox Churches of Antioch and Cyprus are members of the Middle East Council of Churches.

Its North American branch is autonomous, although the Holy Synod of Antioch still appoints its head bishop, chosen from a list of three candidates nominated in the North American archdiocese. Its Australasia and Oceania branch is the largest in terms of geographic area due to the relatively large size of Australia and the large portion of the Pacific Ocean that the archdiocese covers.

The head of the Orthodox Church of Antioch is called Patriarch. The present Greek Orthodox patriarch of Antioch is John X (Yazigi), who presided over the Archdiocese of Western and Central Europe (2008–2013). He was elected as primate of the Greek Orthodox Patriarchate of Antioch and All the East as John X of Antioch (Yazigi) on December 17, 2012. He succeeded Ignatius IV who had died on December 5, 2012. Membership statistics are not available, but may be as high as 1,100,000 in Syria and 400,000 in Lebanon where they make up 8% of the population or 20% of Christians who make up 39–41% of Lebanon. The seat of the patriarch in Damascus is the Mariamite Cathedral of Damascus.

The Greek Orthodox Church of Antioch is one of several churches that lay claim to be the canonical incumbent of the ancient see of Antioch. The Syriac Orthodox Church makes the same claim, as do the Syriac Catholic Church, the Maronite Church, and the Melkite Greek Catholic Church; the latter three are Eastern Catholic Churches in full communion with the Holy See and mutually recognize each other as holding authentic patriarchates, being part of the same Catholic communion. Their fellow Catholic particular church, the Latin Church, also appointed titular patriarchs for many centuries, until the office was left vacant in 1953 and abolished in 1964 with all claims renounced.

According to Luke the Evangelist- himself a Greco-Syrian member of that community:

The disciples were first called Christians in Antioch.