This Guidebook introduces what co-production is: a novel governance method for developing nature-based solutions where there are a lot of actors (individuals, groups or organisations) involved. Co-production is about collaboration, empowerment, and producing shared results, such as policies and visions. The Guidebook covers 1) the outputs and benefits of co-production, 2) principles to define and evaluate co-production processes, and 3) how to design co-production processes step by step.