In this essay I investigate how the Roman colonization (around 50 BC to 400 AD) affected the Celtic religion. I inquire which operators that were behind these changes and under what circumstances they happened. I take a closer look on three places in Gaul and one place and one area in Britain. In my study of these places I see that it was the elite of the Celtic societies who together and under pressure from Rome made these changes. The religion and gods did not change; instead the ritual ceremonies changed to fit into something that Rome thought was right.

Thid thesis concerns pre-Roman religion in Gaul, taking as its starting point Caesar's De bello Gallico. Caesar's account of the Gauls and their religious customs is compared with the accounts of Lucan, Pliny the elder and Ammianus Marcellinus. These are also compared to, and contrasted to, the archaeological evidence. There is some discussion of the nature of the common interpretations of this evidence. The concept of 'the Celts' is touched upon, since much of the relevant evidence has, in our time, been thought of as Celtic.