As with their different languages, the considerable religious differences between the people of the Italic peninsula made up a complex and articulated world. They worshipped different deities, their priesthoods were organised differently, they had different understandings of worship and their votive practices were heterogeneous. There were considerable differences also in the places of worship, which ranged from the great temples of Paestum or Metaponto to the sacred woods of Ariccia or Luco dei Marsi. Local characteristics were long-lasting, even when, from the Fourth Century onwards, major change came about with the growing influence Greek world. Also from this moment, the Roman religion began to permeate the peninsula at a pace which did not directly relate to its military expansion, affecting both very similar societies (such as the Latins or Sabines) and profoundly different ones such as Celts.
The importance of worship for the collective identity of a people, or peoples, can be identified in the circumscribed diffusion of certain deities (such as Angitia or Mephitis for the Oscan-Samnite area) and in the political significance of certain sanctuaries such as, in all likelihood, that of Rossano di Vaglio for the Lucanians. Frequented right up until the time of the emperor Caligula, this sanctuary illustrates how the arrival of the Romans did not necessarily spell an end to the pre-existing religious activities. It was possible to reorganise the areas devoted to worship and identify local gods with Roman deities in a practice known as interpretatio. This is precisely what happened with the deity Reitia, either supplanted or worshipped alongside Minerva.
By no means a unilateral trend, the Romans had in turn received their own influences in the early stages of their history. These include Veiovis, a chthonic figure of probable Etruscan origin which M. T. Varro believes was introduced by the Sabine king Titus Tatius.