While migration and mobility have become crucial themes in the study of the Roman world, their relationship with citizenship has been underestimated and understudied. Yet, migrants were not only foreigners who came to Rome voluntarily or by force. Citizens moved too: those, peasants or new citizens, who had come to settle in the city, or those who emigrated from Rome to a colony in Italy and, later, to a provincial city. What was the impact of this mobility on the conception and practice of citizenship? What did the Romans think of these citizens who travelled or lived abroad?
Such questions make it necessary to distinguish between the period when Rome was still one city among others (6th–3rd centuries) and the period of its conquests, when Rome extended its hegemony through the Mediterranean and became a so-called imperial republic (3rd–1st centuries) before becoming an Empire (27