The development of the Roman Imperial cult — the worship of emperors as divine or semi-divine figures — is one of the more interesting intersections of religion and politics in the ancient world. It was not, as older scholarship sometimes presented it, simply cynical manipulation of popular credulity.

The Eastern Mediterranean had a tradition of ruler worship that predated Rome: Hellenistic kings were routinely worshipped as gods in their lifetimes in the East, though this was alien to Roman tradition. The Roman version was more nuanced: living emperors were officially divine in the East but not in Rome itself; dead emperors were formally deified by senatorial decree (or not — the declaration was not automatic and was sometimes denied to emperors judged to have been bad rulers).

The theological gymnastics required to maintain this distinction — Roman emperor is not divine while alive in Italy, but is worshipped as a god in Asia — were performed with apparent sincerity. Vespasian's deathbed joke ('I think I'm becoming a god') suggests awareness of the performative aspect.

The practical function was primarily political: the imperial cult provided a trans-ethnic religious institution that connected provincial populations to the Roman center. The priests of the imperial cult were provincial elites; their religious role gave them a formal relationship to Roman power that facilitated administrative loyalty.