As global issues have become increasingly complex and interdependent, public-private and multistakeholder partnerships have gained momentum as new mechanisms of governance. This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book elaborates a multifaceted and interdisciplinary conceptualization of partnership effectiveness that should be broadly applicable across different issue areas and levels of governance. It seeks to combine this innovative framework with a mix of interdisciplinary research methods to present new data and case studies on partnership effectiveness. The book focuses largely on partnerships that engage with issues linked to sustainability and sustainable development. It presents empirical analyses that explore a set of crosscutting themes, including the systematic challenges that partnerships encounter and the associated need for adaptability.