Although co-design has been practised in new service and product development for some years, it has only recently begun to appear in the burgeoning field of social innovation. It appears to be well-attuned to this new context, offering as it does an open-ended relational process to generate novel solutions to problems whose very definition seems to escape more conventional approaches. However, even less research attention has been paid to co-design than to social innovation. This book explores the potential of co-design as a social innovation process. It reviews the diverse theoretical and disciplinary foundations on which co-design is based. It proposes a framework for understanding co-design as a cohesive practice across the extremely broad scope of its potential applications. It explores appropriate approaches to governance and evaluation of co-design initiatives and outlines the key issues and limitations on its use. Although it is intended to provide a robust theoretical basis for researching co-design initiatives, it will also be of interest to anyone who is contemplating putting co-design into practice.