Starting from the respective onomastic landscapes of Dionysos and Poseidon, this chapter draws portraits of each god before comparing them. Indeed, as far as divine onomastics, and especially cult epithets, are concerned, points of convergence can be investigated, such as fishing or plant-growing. On the other hand, oppositions are even more representative of the situation of each god in structuring axes of ancient Greek Weltanschauung: Poseidon seems to be very ‘male’ while Dionysos is definitely more mobile between genders; and while the former is deeply rooted in stability and ‘holding together’, the latter makes waves and ‘loosens’. As other deities in a polytheistic system, what distinguishes these two gods is not so much a space (the sea, for example or a domain (such as that of vegetation) as the way in which they invest it. In other words, gods and goddesses of ancient polytheisms can be better understood when looking at their relations with and situations vis-à-vis each other.