This collection seeks to complement and advance recent studies on regionalism in Africa and the implications that this has for the continent’s development. The two case studies on cross-border micro-regionalism in the borderlands of Mali-Burkina Faso and Niger-Nigeria are part of the work of the West Africa Borders and Integration (WABI). WABI is a research institute that looks at cross-border developments in West Africa, particularly at the convergence between political will and regionalisation on the ground. Providing a challenge to the considerable number of state-centric, formalistic and not seldom overly idealistic studies in this field, the two cases show quite clearly that formal borders either essentially do not exist in the Westphalian sense, being ignored by local populations and traders, or, are strategically used by (often self-styled) representatives of the state to extract resources and rents. In either case, the Eurocentric notion of fixed boundaries and bordered delineations has little purchase in the West African Sahel.