Patriarchate (/ˈpeɪtriɑːrkɪt, -keɪt/, UK also /ˈpætri-/; Ancient Greek: πατριαρχεῖον, patriarcheîon) is an ecclesiological term in Christianity, referring to the office and jurisdiction of a patriarch.

According to Christian tradition, three patriarchates—Rome, Antioch and Alexandria—were established by the apostles as apostolic sees in the 1st century. These were officially recognized by the First Council of Nicaea. The Patriarchate of Constantinople was added in the 4th century, and the Patriarchate of Jerusalem followed in the 5th century. These five sees were later recognized collectively as the pentarchy, by the Council of Chalcedon in 451.

Over the course of Christian history, additional patriarchates were gradually recognized by the original ancient episcopal sees. However, several of these later lost jurisdiction—primarily due to the Islamic conquests in the Middle East and North Africa—and became titular or honorary patriarchates, without real institutional authority over their historical territories.

As Christianity expanded throughout the Roman Empire, concentrations of believers were increasingly found in urban centers. Bishops in these cities came to hold pre-eminence in the province where their diocese was located, especially if the city was the provincial capital. Over time, some bishops attained authority beyond their province, becoming recognized as primus inter pares. The Council of Nicea formalized this structure into canon law, following secular Roman administrative patterns. It also introduced the term "Metropolitan" to describe bishops who presided over multiple dioceses within a province.

By the 4th century, cities such as Rome, Alexandria, and Antioch had extended their ecclesiastical authority beyond a single province. For instance, Alexandria held jurisdiction over Roman Egypt, Roman Libya and the Pentapolis, while Rome exercised primatial authority over surrounding provinces within 100 miles (129 km) of the city. By virtue of this multi-provincial oversight, the sees of Rome, Alexandria and Antioch were already exercising a "supra-metropolitan" jurisdiction, later termed as Patriarchates. By the end of the 4th century, all of Italy had come under the broader primatial jurisdiction of the Archbishop of Rome.

After the Imperial capital moved to Byzantium in 330, the renamed city of Constantinople grew in prominence within the Eastern Church. It was granted archiepiscopal status before the Council of 381, which ranked it second in honor after Rome. Archbishop Atticus expanded the jurisdiction of the see in the early 5th century.

Following the Council of Ephesus in 431, Bishop Juvenal of Jerusalem sought to extend his oversight across all three provinces of Roman Palestine, aiming to elevate Jerusalem to a Metropolitan See. This move was opposed by Cyril of Alexandria and Pope Leo I, who argued against separating Jerusalem from the authority of Antioch. Juvenal later claimed metropolitan authority over Roman Arabia and Phoenicia. At the Council of Chalcedon, negotiations with Archbishop Maximus of Antioch led to approval for Jerusalem's oversight over all of Palestine, but not beyond. The council recognized Jerusalem as a Metropolitanate, elevating it alongside the sees of: Rome, Constantinople, Alexandria and Antioch. Emperor Justinian would later recognize Jerusalem as one of the five official Patriarchates.

The East–West Schism of 1054 separated the Latin Church’s See of Rome from the Byzantine patriarchates of the East, resulting in the formation of the modern Catholic Church and Eastern Orthodox Church. ^{[citation needed]}