This Handbook seeks to be the definitive reference for the large and growing field of Open Innovation. A comprehensive collection of short and authoritative chapters, the volume summarizes the most vital research published in Open Innovation. It is an essential reference for seasoned scholars, a welcome introduction for junior scholars, and a kick-start package for undergraduate and MBA students. Four editors, 75 reviewers, and 136 contributors collaboratively developed 57 chapter handbook chapters. These present the current state of the art featuring academic theory and managerial practice as well as the outlook for how open innovation should be further developed. The empirical, conceptual, and practical insights of the handbook highlight the importance of strengthening practice-inspired research and purposeful knowledge exchanges between individuals, organizations, and ecosystems.