'''''Episcopi vagantes''''' (Latin for "wandering bishops") are persons who have been [[ordination|ordained]] as [[bishop]]s in some irregular fashion, especially those claiming to have valid [[Roman Catholic Church|Roman Catholic]] orders although their ordinations were not authorized by the Roman Catholic Church.
The Vatican considers some such ordinations "valid" but "unlawful," but the Orthodox Church considers them
to simply not be ordinations and thus also considers persons so ordained not to be bishops at all. This is because unlike the Vatican, it considers [[apostolic succession]] to exist only in bishops who are regularily ordained by bishops that are neither themselves defrocked, nor teach heretical teachings. Holy Orders are not regarded by the Orthodox as "indelible," thus if a bishop breaks from the Church, his episcopacy (and thus his ability to ordain) does not follow him.
Many of these claim succession from the see of Utrecht, or from Orthodox or [[Eastern Rite Catholic]] churches; others from Roman Catholic bishops that have ordained their own bishops after disputes with the Vatican. Such lines continue to persist because of the more mechanistic understanding of apostolic succession which the Roman Catholic Church has—that is, if a "valid" bishop ordains a man using the proper rituals, then he is "valid" as well, even if neither has any living connection to the Church. The Orthodox understanding, however, necessarily presupposes the impossibility of ''episcopi'' that are ''vagantes'', for the ministry of the episcopacy resides only ''within'' the Church.
Many ''episcopi vagantes'' will style their churches variously as ''Orthodox'', ''Catholic'', ''Apostolic'', or any of the other historical names used by the Church.
In modern times, some of the major lines of ''episcopi vagantes'' trace their succession to A. H. Mathew (deposed from the Old Catholics), J. R. Vilatte (variously Roman Catholic, Old Catholic, and with
an alleged line from a non-Chalcedonian Syrian bishop), and [[Aftimios Ofiesh]], a 20th century Syrian bishop serving under the auspices of the [[Church of Russia]] in America, who was deposed for marrying a woman under his care.
*Many people have claimed ordinations as bishops where it is questionable whether the ordination ever actually took place, which is a separate issue.
Further, bishops belonging to groups which are in [[ schism]] (i.e., out of [[full communion]]) or have suspended [[concelebration]]s are not ''episcopi vagantes'' inasmuch as their consecrations as bishops were clearly within the Church and the break in communion may well only be temporary.
*''The Oxford Dictionary of the Christian Church, 3rd ed.'', pp. 555, 1054, 1698