Arval Brothers, in ancient Rome, college or priesthood whose chief original duty was to offer annual public sacrifice for the fertility of the fields. The brotherhood, probably of great antiquity, was almost forgotten in republican times but was revived by Augustus and probably lasted until the time of Theodosius I. It consisted of 12 members, elected for life from the highest ranks, including the emperor during the principate. Literary allusions to them are scarce, but 96 of the acta, or minutes, of their proceedings, inscribed on stone, have been discovered in the grove of the Dea Dia near Rome.