In this workshop we will critically engage with the different aspects, applications, and implications of circularity and ask: Is circularity a principle of sustainable HCI? In order to answer this question, the workshop combines a variety of methods. The starting points for this exploration are the artifacts that the participants will present in a ‘show and tell’ session. These artifacts represent each participant’s work or interest in sustainable HCI, as well as an idea or form of circularity. Through two more exploratory sessions, we will give form and shape to what circular thinking can contribute to sustainable HCI. In the final session of the workshop we will map our findings on the most iconic digital device of our time, the mobile phone. Acknowledging the central role of design in the sustainability of products and services, we will end our workshop with a final question: who and what will benefit from this re-design?