This book provides an introduction to the concept of Social Innovation for readers interested in social and public policy. It explains why social and public policy analysts, policy makers and practitioners should become familiar with this idea, and explores how social innovation relates to key debates and core issues in public welfare. The book explains how social innovation relates to more familiar concepts, such as entrepreneurship, technological and business innovation and social enterprise. It discusses the social and economic challenges behind the growing interest in social innovation across the world. It illustrates the distinctive characteristics of social innovations through case studies which demonstrate how they address such issues as social isolation and mental health, childcare, education, homelessness, integrating migrant communities and financial exclusion. The book discusses in detail how social innovations address social problems in three substantive areas: food poverty, care provision and employment. It draws upon comparative research evidence to outline and analyse how social innovations have developed inventive responses to these complex challenges, and assesses their respective impact on well being. The book concludes by discussing the implications of social innovation for existing social welfare systems and social citizenship rights. It highlights some of the questions raised by social innovation for social and public policy reform and identifies potential limitations and concerns. It argues that those with an interest in social welfare policy should critically engage with the arguments for and evidence relating to social innovation.