This book describes the important role played by communities in innovation processes and how organizations can benefit from it. A community brings together individuals who share a common passion for a given area of knowledge and can contribute to innovation at different levels: capitalization of good practices, problem solving, sharing of expertise, or development of new and creative ideas. The literature has progressively identified many variants of communities such as communities of practice, epistemic communities, communities of interest, virtual communities, etc. These forms of communities differ regarding the type of the specialized activities of knowledge on which they focus. As practitioners and academics increasingly emphasized the needs of collaborative approaches in innovation, they progressively challenged the traditional idea that innovation is mainly generated by hierarchical corporate departments and highlighted the active role that communities play in innovation processes. The aim of this book is to shed light, using multiple examples, on the proactive and fundamental role of communities in the new innovation practices of organizations.