Most research on Offa’s Dyke has focussed on the political, social and landscape contexts of the time in which it is presumed to have been built, namely the late-eighth century. However work on Offa’s Dyke – and indeed other medieval linear earthworks – has entirely ignored the increasingly well-developed theoretical perspectives in the field of contemporary border studies. Here it has been argued that borders and border monuments should be viewed less as markers of division and more as mechanisms of connectivity and encounter; borders are liminal spaces, providing means of passage and facilitating the creation of cross-border networks. Borders – whether real or imagined – create a ‘borderland’: an area which is administratively and politically connected to one polity, but which comes under strong economic, cultural and demographic influences from another. This paper looks afresh at Offa’s Dyke from these theoretical perspectives and argues that the construction of the Dyke was part of a deliberate programme to create such a ‘borderland’ landscape. In the event this did not benefit the kingdom of Mercia, but it did generate a distinctive cultural and physical landscape which influenced political and social change for the next thousand years.