Voice is a term that has been widely used in the practitioner and academic literature on human resource management (HRM) and industrial relations in recent years. Freeman and Medoff (1984) associated voice with union representation and in particular with the role of unions in articulating concerns on behalf of the collective. As union density has fallen in recent years, analysis of voice in workplaces has often focused on how workers communicate with managers and are able to express their concerns about their work situation without a union, and on the ways in which employees have a say over work tasks and organizational decision-making. But researchers from different disciplinary perspectives often use voice in different ways. Some refer to involvement, others to participation, while yet others refer to empowerment or engagement as if they are interchangeable. As Kaufman (Chapter 2) makes clear, few appreciate the historical pedigree of employee voice, for instance, where Karl Marx and Adam Smith expressed interest in the ways and means through which labour expressed its voice. The deeper antecedents to voice have often been forgotten or eclipsed in a rush towards newer managerial fads, such as engagement or other equally abstract notions of labour offering discretionary effort. This book presents analysis from various academic streams and disciplines that illuminate our understanding of employee voice from these different perspectives. The following chapters show that research on employee voice has gone beyond union voice and non-union voice to build a wider and deeper knowledge base. As the introduction to the book, this chapter provides a guide to the debates about the different dimensions of employee voice and to the research findings in different areas. We review the meanings and purposes surrounding the definitions of voice; consider the role of key actors in the workplace; and evaluate the different forms and processes of voice in different spheres, contexts and organizational settings. We hope that the book will help the reader understand the debates associated with employee voice and appreciate the contribution of the different approaches to our understanding of what goes on in the workplaces that are at the heart of modern economies.