This research work addresses the question of the origins of the Samothracian Mysteries. It is done from a new and multidisciplinary perspective; since, in addition to the foreign information and opinions of the authors of Antiquity, for the first time it takes into account the archaeological, epigraphical, numismatical and iconographical testimonies from the island itself. It examines its territory (the island and its surroundings, the myths and legends, the toponymy), its cult (the theories about its foundation, the sanctuary, the gods) and its history (from the Neolithic to the Iron Age), to find out which populations dwelled on Samothrace before it was colonized by the Greeks; in order to discover the culture they would have encountered and from which they would have inherited their cult. It reaches the conclusion that this culture was the Thracian; and that, originally, at the Samothracian mystery cult were venerated the Thracian “Mother of the Gods” and Sabazius.