The pontifex maximus was the chief high priest of the College of Pontiffs in ancient Rome. This was the most important position in the ancient Roman religion, open only to patricians until 254 BC, when a plebeian first held this position. Although in fact the most powerful office in the Roman priesthood, the pontifex maximus was officially ranked fifth in the ranking of the highest Roman priests, behind the rex sacrorum and the flamines maiores.

Religion in ancient Rome consisted of varying imperial and provincial religious practices, which were followed both by the people of Rome as well as those who were brought under its rule.