Addressing urgent environmental concerns, such as climate change, biodiversity loss, water scarcity and marine plastics, requires rapid responses. We need novel solutions that are circular by design and have the potential to change our mode of operation more rapidly and systematically.To understand and re-design our material cycles to be circular, we need data and systems understanding. Currently this data is scattered and siloed in many forms and formats, making its use difficult for individual decision makers.The Circular Design Network project (2019-2022) was initiated to understand the practical data needs and gaps at the systems level, and to build a stakeholder network to develop data approaches for circularity. By building a network that comprises data users, providers and developers, we aim to develop new ways of collecting and validating data, along with new methods to process and refine it into system-level models of action. This guide is meant as an open invitation to participate in building a circular economy based on shared data and knowledge. It also introduces central concepts, approaches and tools for data-enabled circular design, illustrating value creation from data to knowledge to action. These concepts are concretized through case examples in the battery, textile and food value chains.