An ecclesiastical province is a large jurisdiction of religious government within the Orthodox Christian Church, so named by analogy with the secular Roman province during centuries of the early Church.
As the early Church grew generally within the territorial limits of the Roman Empire, the Church adopted for its organizational structure the terminology and geographical structure of the Empire. The form of the ecclesiastical provinces first began to become fixed in the eastern part of the Roman Empire where many of the more important political centers of the Church developed. The centers included Antioch, Syria, the Province of Asia, and Alexandria as well as Rome and Carthage in the West. As missionaries traveled from these centers preaching the Gospel, they regarded the centers as the mother churches of the newly founded Christian communities.
From the second half of the second century, the bishops of the territories within the same geographical and often political boundaries became accustomed to assemble on important occasions for common counsel in synods. From the end of the second century the summons to attend these increasingly important synods was usually issued by the bishop of the capital of the civil province (eparchy), who also presided over the synod. This was especially true in the East. Thus, in the East during the third century the bishop of the provincial metropolis came gradually to occupy a certain superior position and received the title of metropolitan.
At the Council of Nicea in 325 the position of the metropolitan was taken for granted and became the basis for conceding to him definite rights over the other bishops and dioceses of the civil province. In Eastern canon law since the Synod of Antioch of 341 (canon 9), it was a principle that every civil province was likewise an ecclesiastical province under the direction of the bishop of the provincial capital, the metropolitan.
In the Western Roman Empire the formation of ecclesiastical provinces did not develop as early as in the East. While the Bishop of Carthage began to be recognized as the primate of the dioceses of Northern Africa in the third and fourth centuries, it was during the fourth century that metropolitans of the separate provinces in Spain, Gaul, and Italy gradually appeared, although the boundaries of these provinces did not coincide with those of the empire. The migration of the Germanic tribes, however, prevented stable formation of ecclesiastical provinces in the West as in the East until after the fifth century when such development gradually occurred, generally in accordance with the old divisions of the Roman Empire. By the end of Antiquity the existence of church provinces as the basis of ecclesiastical administration was fairly common in the West.
As the Orthodox Christian Church has expanded over the world, beyond the ancient limits of the Roman empire, the concept of having the ecclesiastical boundaries follow the civil boundaries has continued, taking in account of the size of the successor civil and national entities. In the church structures, all parishes belong to an eparchy, the equivalent of a diocese, which is governed by a bishop. While there are exceptions, eparchies generally follow civil boundaries. Eparchies are part of an autonomous or autocephalous church, headed by an archbishop, metropolitan or patriarch depending on the status of the particular autonomous or autocephalous church.