What was the title of the high priest of Jupiter in ancient Rome?

The Flamen Dialis was the title of ancient Rome’s high priest of Jupiter.

The name Dialis derives from Diespiter, an old Latin form connected with Jupiter. The office belonged to the three flamines maiores, priests who served the principal gods of the Archaic Triad: Jupiter, Mars, and Quirinus. Tradition attributed the creation of these offices to Numa Pompilius, Rome’s second king.

The Flamen Dialis faced unusually strict religious rules. He could not touch metal, ride a horse, see a corpse, or spend a night away from Rome. These restrictions symbolized his constant ritual availability to Jupiter. His wife, the Flaminica Dialis, also had important ceremonial duties.

A common mix-up is the Pontifex Maximus, who eventually became the leading figure in Rome’s priestly administration. The Rex Sacrorum ranked above the Flamen Dialis in the formal priestly order, but the Flamen Dialis was specifically Jupiter’s high priest.