This thesis argues that the scale of independently motivated geographical mobility within Italy during the 3rd-1st centuries BC was much greater than is usually thought, and that the impact of this type of movement on political developments was correspondingly more significant. The study of this private phenomenon, affecting the demographic face of Italy independently of Roman state control, also provides a new perspective on the wider process of transformation in this period, restoring as it does the element of individual choice. The thesis begins by distinguishing the type of independent mobility in which it is interested from other types of population movement in the same period, before providing a brief review of work on mobility in Roman Italy and other parts of the Mediterranean world. Chapter 2 examines the various types of evidence for the phenomenon: literary, epigraphical, and archaeological. Two central chapters exemplify the phenomenon - and its connection to economic change - using the full range of literary, epigraphical, and archaeological evidence to reveal patterns of mobility in two chosen areas: southern Latium, with the focus on the two important sites of Minturnae and Fregellae, and the region of the Po Valley. The final section examines the relationship between the picture of a high level of mobility, as revealed in the case studies, and the political context of Roman rule in Italy in the middle Republic. First, it is argued that the so-called ius migrandi never existed as a privilege of the Latins, but was instead a restriction placed on colonies to maintain their demographic stability. Second, it is suggested that the difficulty of preventing individual migration had seriously disruptive consequences, especially for communities suffering from emigration in the 2d century, which in turn contributed significantly to the strain on Rome's middle Republican framework of control in Italy.