This paper by Ignacio Mas and others reviews the growing literature that has spawned around branchless and mobile banking in developing countries over the last five years. Around 2.6 billion people in the world do not have access to formal financial services, and yet 1 billion of them have a mobile phone. Branchless banking systems take advantage of increasingly ubiquitous real-time mobile communications networks to bring banking services into everyday retail stores, thereby alleviating the lack of banking infrastructure in the communities where poor people live and work. Most deployments are quite recent, and hence there is a shortage of hard empirical evidence relating to them. One mobile banking scheme in particular, M-PESA in Kenya, has shown phenomenal success, and has been a catalyst for much of the research. Here we review the emerging literature in terms of the definitions and model taxonomies employed; the status and drivers of global adoption of these schemes; the take-up and usage patterns of customers, and their socio-economic impacts; and the regulatory issues. Our twin objectives with this paper are to stimulate further research on these questions and to help policymakers and practitioners focus their continued efforts in creating an enabling environment for branchless banking.