Sustainable development, including how to involve stakeholders in deciding the future for the land where they live or work, is a crucial current issue. However, the meanings given to both terms – development and sustainable – are so diverse and controversial that a clear methodology is required to establish participatory approaches for the management of renewable natural resources. Companion modelling is one such approach. It is unique in its continuing involvement of stakeholders throughout the approach, the use of models as a way of eliciting representations of the issues at stake and the priority given to the collaborative understanding of the outputs from these models. The book introduces the companion modelling approach by presenting the stance that underpins it, the methods and tools used with stakeholders and the specific role of models during the process. It addresses the means to deal with the different levels of decision-making and to take into account the various power relationships. It proposes a methodology to assess the impact of the approach on the stakeholders involved in the process. The book includes 27 case studies and 7 teaching tools that describe the successful use of the approach in a variety of settings or teaching contexts. It is intended for researchers working on rural development or renewable resources management, as well as students and teachers.