This chapter argues that population mobility was central to the development of medieval urban society, environment and institutions. The first part provides an overview of the changing extent and nature of English urbanisation in the centuries between 600 and 1500, and addresses both mobility and migration within England, and beyond England. It outlines some of the multi-disciplinary and conceptual approaches underpinning this work and then focuses in greater depth on urban migration fields, and on the infrastructure, regulation, and experience of urban mobility. The chapter identifies competing cultural contexts within which values associated with urban mobility were conceived, and argues that both political language and developing social customs concerning the regulation of mobility were central to the experience of migrants.