Understanding the interaction between cooperation and conflict in establishing effective social behaviour is a fundamental challenge facing societies. Reflecting the breadth of current research in this area, this volume brings together experts from biology to political science to examine the cooperation–conflict interface at multiple levels, from genes to human societies. Exploring both the exciting new directions and the biggest challenges in their fields, the authors focus on identifying commonalities across species and disciplines to help understand what features are shared broadly and what are limited to specific contexts. Each chapter is written to be accessible to students and researchers from interdisciplinary backgrounds, with text boxes explaining terminology and concepts that may not be familiar across disciplinary boundaries, while being a valuable resource to experts in their fields.