Celtic tribes once occupied a vast area which stretched from Ireland to Spain and northern Italy, down the Danube river to the Balkans. Even in Asia a small province named Galatia was held by the Galati, who were of Celtic origin and survived till late antiquity. Throughout these territories we find many archaeological traces of ancient Celtic religion. Highly important for the reconstruction of the Celtic pantheon are the widespread epigraphic testimonies on various votive objects from Celtic sanctuaries and shrines (e. g.: altars, columns, bronze tablets etc.) as well as the anepigraphic reliefs representing indigenous deities. With the ever increasing number of such significant finds this invaluable epigraphic source material has never been documented, analysed or interpreted in its entirety. Scholarly documentation, systematic analysis are nevertheless an essential premise to study ancient Celtic religion. It will not only allow us to recognise the linguistic origins, the meaning and the spread of Celtic deities, but will also improve our understanding of the phenomenon of interpretatio Romana/Celtica and the process of Romanisation of Celtic societies as a whole.