The influential are no longer only those with celebrity status - but until now there has been no authoritative resource on the theory and practice of influencer marketing. This book will educate and inspire decision makers, researchers, students, and influencers themselves. Diving deeper than the many "how-to" books on the influencer phenomenon, this book brings in frameworks from marketing, sociology, psychology, and communication studies to redefine the influencer as a persona (related to a person, group of people, or organization) that possesses greater than average sway over others. Cornwell and Katz go on to: introduce the influencers, macro and nano, authentic and inauthentic, ascending and fading consider their relationship to brands in the marketing ecosystem, along with regulations that set limits on influencer marketing describe how influence is measured and evaluated and look into the future; and bring together the latest research on influencer marketing and organize it for the reader The book serves both those who want to understand the science behind influencer marketing and those who want to most effectively employ influencers in brand strategy. Instructors, students, and professionals will appreciate international examples from multiple industries applying theories to the real world.The Open Access version of this book, available at http: //www.taylorfrancis.com, has been made available under a Creative Commons [Attribution-Non Commercial-No Derivatives (CC-BY-NC-ND)] 4.0 license.