The fundamental question uniting the contributions to this volume is: what exactly is populism? This is certainly not a new question, as a large amount of literature has focused on this topic for more than half a century. As little conceptual consensus has been reached so far, this book aims to reduce the level of abstraction. To this end, it approaches the populist phenomenon from a broader theoretical and empirical perspective, making reference to its developments on several continents. The book is divided into two parts: the first is theoretical and discusses various perspectives on populism, while the second is empirical and emphasises the diversity of the forms populism has embraced throughout the world. Without aiming to solve old dilemmas, to cover all the existing forms of populism, or to outline unequivocal conclusions, the contributions to this book fulfil a twofold task. On the one hand, they help to clarify theoretically a concept that is difficult to grasp and use. On the other hand, by way of reflecting these difficulties, they present several forms of populism worldwide. Their main purpose is to highlight the differences between the continents. Each of the chapters in the second section successfully accomplishes this, providing an overview that is useful both in analysing populism and in identifying the populist elements in national and international political actions or discourses.