In ancient Roman religion, a flamen was a priest assigned to one of fifteen deities with official cults during the Roman Republic. The most important three were the flamines maiores (or "major priests"), who served the three chief Roman gods of the Archaic Triad. The remaining twelve were the flamines minores ("lesser priests"). Two of the minores cultivated deities whose names are now unknown; among the others are deities about whom little is known other than the name. During the Imperial era, the cult of a deified emperor (divus) also had a flamen.
The fifteen Republican flamens were part of the Pontifical College which administered state-sponsored religion. When the office of flamen was vacant, a pontifex could serve as a temporary replacement, although only the Pontifex Maximus is known to have substituted for the Flamen Dialis.
The official costume of a flamen, of great antiquity, was a hat called an apex and a heavy woolen cloak called a laena. The laena was a double-thick wool cloak with a fringed edge, and was worn over the flamen's toga with a clasp holding it around his throat. The apex was a leather skull-cap with a chin-strap and a point of olive wood on its top, like a spindle, with a little fluff of wool at the base of the spindle.
By the time of the religious reformation of Augustus, the origins and functions of many of the long-neglected gods resident in Rome was confusing even to the Romans themselves. The obscurity of some of the deities assigned a flamen (for example Falacer, Palatua, Quirinus and Volturnus) suggests that the office dated back to Archaic Rome. Many scholars assume that the flamines existed at least from the time of the early Roman kings, before the establishment of the Republic. The Romans themselves credited the foundation of the priesthood to Numa Pompilius, the second king of Rome. According to Livy, Numa created the offices of the three flamines maiores and assigned them each a fine robe of office and a curule chair. The flamines were circumscribed by many taboos.