legatus

Legatus is a Latin noun meaning envoy, ambassador, or delegated official. In ancient Rome, legatus designated a person entrusted with authority by a higher authority, often to act in a commander’s name or to govern in the emperor’s stead. The term underpins several Roman ranks and offices and is the source of English legate, legation, and related terms.

In the military sphere, the most prominent appointment was legatus legionis, the commander of a legion, usually a senator of consular or praetorian rank appointed by the emperor. Legati also served as deputies and staff to provincial governors, and could command auxiliary forces or observe campaigns in the field. Their role combined military command with political and diplomatic functions and commonly required imperium.

In provincial administration, legatus Augusti pro praetore governed imperial provinces, often with one or more legions stationed there when required. In the Republic, legati could accompany commanders or serve as emissaries; in the Empire, the title became a formal rank for high-ranking officials and diplomats, distinct from proconsuls who governed senatorial provinces.

In the Christian church and in modern diplomacy, a legatus or legate is a personal representative sent by a pope or head of state. Papal legates, apostolic legates, and diplomatic legates operate in a variety of capacities, sometimes with plenary powers (legate a latere) or with more limited authority. The term survives in English and other languages primarily as legate or legation, denoting the office or the people involved.