in Christianity, a bishop without authority or without recognition in any major Christian church. Such bishops may have been properly consecrated but were not assigned to a diocese or were deprived of their diocese for some reason or were excommunicated by their church; or they may have received an irregular consecration by another bishop.

In the early Christian church, wandering bishops were a problem, primarily because some bishops were consecrated but were not given jurisdiction over a diocese. In addition, theological controversies in the 4th and 5th centuries often resulted in bishops being deprived of their sees; they retained their consecration as bishops but had to wander to make a livelihood. In later times, the number of episcopi vagantes was increased by bishops driven out of their dioceses by war, especially in Spain, or by bishops consecrated for dioceses controlled by Muslims who would not allow Christian bishops to take up residence. The activities of episcopi vagantes were not restricted in the Roman Catholic church until after the Council of Trent (Trent, Council of) (1545–63).

In modern times, however, many episcopi vagantes have appeared who are outside the control of any ecclesiastical authority. Most of these wandering bishops trace their succession to one of three men consecrated in the late 19th and early 20th centuries. The first of these was Jules Ferrette, a former Roman Catholic priest who was consecrated in 1866 by the Jacobite bishop of Homs (Emesa) in Syria; he worked in England and the United States. Joseph René Vilatte, a lapsed French Catholic who had worked in the Protestant Episcopal Church in Wisconsin, was consecrated in 1892 by the Metropolitan of the Independent Catholic Church of Ceylon, Goa, and India; he worked in the United States. Arnold Harris Mathew, a former Roman Catholic priest, was consecrated in 1908 in Utrecht, Neth., by Old Catholic bishops. His consecration was later described as having been obtained by misrepresentation, and he was repudiated by the Old Catholics. He tried unsuccessfully to create an Old Catholic movement in England.