A papal legate, from the Decretals of Boniface VIII (1294 to 1303). British Museum, 23923.
A papal legate – from the Latin, authentic Roman title Legatus – is a personal representative of the pope to foreign nations, or to some part of the Catholic Church. He is empowered on matters of Catholic Faith and for the settlement of ecclesiastical matters.
The legate is appointed directly by the pope (the bishop of Rome and head of the Catholic Church). Hence a legate is usually sent to a government, a sovereign or to a large body of believers (such as a national church) or to take charge of a major religious effort, such as an ecumenical council, a crusade to the Holy Land, or even against a heresy such as the Cathars.
The term legation is applied both to a legate's mandate and to the territory concerned (such as a state, or an ecclesiastical province). The relevant adjective is legatine.
There are several ranks of papal legates, some of which no longer exist today:
The most common form of Papal Legate today is the Apostolic Nuncio, whose task it is to strengthen relations between the Holy See and the Roman Catholic Church in a particular country and at the same time to act as the diplomatic representative of the Holy See to the government of that country.
For countries with which the Holy See has no diplomatic relations, an Apostolic Delegate is sent to serve as a liaison with the Catholic Church in that country, though not accredited to its government. (see Nuncio)
Legatus a Latere
This highest rank (literally "from the (Pope's) side", i.e. "intimately" trusted) is normally awarded to a priest of cardinal rank. It is an exceptional investiture and can either be focused or broad in scope. The legate a latere is the alter ego of the Pope, and as such, possesses full plenipotentiary powers.
Internuncio – a lower rank than Nuncio for a papal diplomatic representative, a title historically used at a time when states sent to some less important countries diplomatic representatives, called Envoys or Ministers, lower in rank than Ambassadors.