any of a body of 20 Roman priestly officials who were concerned with various aspects of international relations, such as treaties and declarations of war. The fetials were originally selected from the most noble families; they served for life, but, like all priesthoods, they could only submit advice, not make binding decisions.

According to Book 1 of Livy's history of Rome, after Rome had been injured by another state, four fetials were sent out to seek redress. One member, the verbenarius, carried herbs gathered from the Arx on the Capitoline Hill. Another member, called the pater patratus, served as the group's representative. Upon reaching the border of the offending state, the pater patratus first announced his mission and addressed a prayer to Jupiter in which he affirmed the justness of his errand. Crossing the border, he repeated the same form several times. If, after 30 days (some sources give 33), no satisfaction was given, the pater patratus harshly denounced the offending state and returned to Rome, where he reported to the Senate. If Rome decided to wage war, the pater patratus returned to the border, pronounced a declaration of war, and hurled across the boundary either a regular spear or a special stake sharpened and hardened in the fire. This ritual was supposed to keep Rome from waging an unjust or aggressive war. If, however, the hostile country was far away, the spear soon came to be cast upon a piece of land in front of the Temple of Bellona in Rome; by a legal fiction, that land was treated as belonging to the enemy. Thus the ritual limitations were overcome by such legal fictions, and the state entered into any wars that were seen to be to its advantage.

When treaties were concluded, the verbenarius and the pater patratus were sent to the other nation; after reading the treaty aloud, they pronounced a curse on Rome should that state be the first to break it. The ceremony was concluded by killing a pig with a flint implement. By the time of the late republic, the institution had faded out, although the emperor Augustus (63 BC–AD 14) revived the group, ceremonially at least, and became a member himself in his effort to restore old Roman traditions.