An apostolic prefect or prefect apostolic is a priest who heads what is known as an apostolic prefecture, a 'pre-diocesan' missionary jurisdiction where the Catholic Church is not yet sufficiently developed to have it made a diocese. Although it usually has an (embryonal) see, it is often not called after such city but rather after a natural feature, or administrative geographical area, which may be a name in use by the local inhabitants, or one assigned by a colonial authority, depending on the circumstances under which the prefecture was established.
If a prefecture grows and flourishes, it may be elevated to an apostolic vicariate, headed by a titular bishop, in the hope that with time the region will generate enough Catholics and stability for its Catholic institutions, to warrant being established as a diocese. Both these stages remain missionary, hence exempt, that is, directly subject to the Holy See, specifically the Dicastery for Evangelization, rather than, as a diocese normally would, belong to an ecclesiastical province.
