Pontifex Maximus

the chief high priest of the College of Pontiffs in ancient Rome, open only to patricians until 254 BCE, when a plebeian first occupied this post; gradually became politicized until, beginning with Augustus, it was subsumed into the Imperial office

The Pontifex Maximus was the high priest of the Roman Republic and Empire. The words meant 'greatest bridge-builder'. It was a religious post under the Roman Republic, and a mostly ceremonial post under the Roman Empire. The term was later used in the Roman Catholic Church for the Pope.