This book surveys the state of knowledge regarding development and humanitarian non-government organisation (NGO) responses to preventing and countering violent extremism (P/CVE). It delineates the nexus and shared objectives between P/CVE and development/humanitarian NGO frameworks and outlines a reframing of the concept of VE into violent and hateful extremism (VHE) as a shift to a more nuanced understanding which addresses inherent complexities and entanglements more deeply. The diversity of case studies, datasets, and author perspectives serves to advance knowledge on this topic and provide useful evidence and insights to inform policy and practice. This book will be a valuable resource for students, academics and professionals interested in international humanitarian, development operations and conflict resolution. The chapters in this book were originally published as a special issue of Conflict, Security & Development.