Roman armies operated for the first time west of the Alps in around 150 BC, to provide assistance to the allied city of Massalia (Marseille) (Polyb. 33.8–10). More decisive campaigns took place during the 120s BC and the 100s BC. There are few archaeological traces of these military operations, however, and their interpretation is ambiguous. From the western Alpine arc to the Pyrenees, huge areas of southern Gaul seem to have been excluded from having a Roman presence until the last decades of the Republican period. The second half of the 2nd century BC and the first third of the 1st century BC were nevertheless a decisive turning point in the economic and monetary history of the Mediterranean Celtic region as a whole (Garcia 2014). In a context of increasing monetisation of local economies, the intensification of production activities and the reconfiguration of major transregional trade networks led to the adoption of new monetary references. These changes were initially the product of external trends, but were boosted by the economic dynamism that characterised the Celtic region as well as the Mediterranean basin and its fringes. On the ground, it was Italian private economic agents, rather than the representatives of the Roman city, who seem to have been the privileged partners of the indigenous elites and the first beneficiaries of this reorganisation of trade, which began in the mid-2nd century BC. The goal of this chapter is to highlight the contributions of the concept of ‘connectivity’, instead of that of conquest, in understanding the changes that affected monetary activities in southern Gaul between c. 150 BC and c. 70 BC. The objective will be to have a more precise view of the respective amount and diversity of action by Rome, by Italian firms and by local stakeholders. The chapter begins by characterising the main endogenous monetary dynamics that can be observed in southern Gaul during this period. This is followed by an assessment of how foreign currencies entered the area. There is then an attempt to define a new model to facilitate an understanding of how Rome intervened in local monetary activities.