A territorial abbey (or territorial abbacy) is a particular church of the Catholic Church comprising defined territory which is not part of a diocese but surrounds an abbey or monastery whose abbot or superior functions as ordinary for all Catholics and parishes in the territory. Such an abbot is called a territorial abbot or abbot nullius diœceseos (abbreviated abbot nullius and Latin for "abbot of no diocese"). A territorial abbot thus differs from an ordinary abbot, who exercises authority only within the monastery's walls or to monks or canons who have taken their vows there. A territorial abbot is equivalent to a diocesan bishop in Catholic canon law.
While most belong to the Latin Church, and usually to the Benedictine or Cistercian Orders, there is one Eastern Catholic territorial abbey: the Italo-Albanian Greek Catholic Abbey of Grottaferrata. The closest equivalent in the Eastern Orthodox Church would be a stauropegion (e.g. most famously, Mount Athos).
