Abstract:The Middle class as a concept has evolved over time, taking on various meanings at various points throughout history, becoming an object to aspire to for poor people, an object of desire for a strong government, a buzzword for politicians the world over, and the source of new customers for firms, and the global economy more broadly. This special issue of Poverty in Focus, exclusively devoted to the exploration of themes related to the middle class is part of a larger endeavour initiated by The International Policy Centre for Inclusive Growth (IPC-IG), in collaboration with the Secretariat for Strategic Affairs of the Office of the Brazilian Presidency, to explore the middle class within a development context at national, regional and international levels. Contributions to this middle-class-themed issue have come from leading scholars and development practitioners from across the globe who have addressed the phenomenon of the middle class from several different ideological, academic and regional perspectives to explore a variety of issues in relation to the significance of a growing middle class and overall development achievements. The middle class is a highly contested concept as is evident by the diversity of its many definitions. Contributing authors here seek to navigate this unstable terrain; at times utilizing, and at others critiquing the prominent sociological and income-based definitions while being mindful of the middle classes? historically and culturally specific realities. For policy-guided purposes, although quantitative-based approaches to define the middle class may seem to be directly applicable and appropriate for the context, it is also important to bear in mind that they sometimes require a further analysis to address definitional or operational aspects otherwise left out of income-based (quantitative) approaches. Income-based approaches in general reflect the middle of an income distribution (i.e., the middle class as the middle third of an income distribution), yet they all too often do not take into account many of the socio-cultural, psychological and, in some cases, political aspects of being a part of the middle class. When speaking about the middle class, one must determine the reason or objective for trying to define the concept in the first place. It seems as though the term is quite relative, as incomebased cut off points and conceptions can be easily adapted. However the usefulness of infusing development discussions with examinations of a clearly defined middle class is not to be ignored. Those that are out of poverty but not yet economically secured in the middle class (via a definition of middle class based on economic security) as highlighted by several articles in this publication, form a group that is of significant importance to ensure development gains are not lost and that this very vulnerable group is enabled to continue to develop socio-economically towards entering such a middle class. The past decade and a half of economic growth that has been experienced in the emerging economies of Brazil, Russia, India, China and South Africa (the BRICS nations), among others, has attracted much international investment, finance and social development attention, particularly to the regions that have lifted many people out of poverty throughout the same period. The growth of the middle class within such societies has also attracted much attention, and has been considered a segment of the global population that is set to be a new driver of the global economy. The relevance of such a segment of society in securing development gains, and its role in development more broadly remains a highly debated topic, reflected in the diversity of articles included in this issue. This special issue introduces the reader to a variety of ongoing discussions while helping to raise a number of salient questions about the role of the middle class in development, among other questions such as: Will this rising middle class align its interests with the poor and vulnerable of society or with those of the wealthy? Is the middle class a force that strengthens democratic institutions? In developing countries will this rising middle class demand better quality and a larger quantity of public services from their governments? Or, will they increasingly opt out of public options, for services provided by the private sector (i.e., private health care, private schools etc.)? On behalf of all of us here at the IPC-IG, I hope that the following set of articles exploring the different facets of the middle class, will help to inform readers of the complexity of trying to define the middle class as a quantitative grouping as well as a sociological phenomenon, and that they serve as a good introduction to the ongoing debates about the middle class within discussions concerning poverty reduction, democracy, civic action, economic growth and development more broadly.