Design is conventionally considered to be about making and creating new things. But what about the converse of that process – unmaking that which already exists? Researchers and designers have recently started to explore the concept of “unmaking” to actively think about important design issues like reuse, repair, and unintended socio-ecological impacts. They have also observed the importance of unmaking as a ubiquitous process in the world, and its relation to making in an ongoing dialectic that continually recreates our material and technological realms. Despite the increasing attention to unmaking, it remains largely under-investigated and under-theorized in HCI. The objectives of this workshop are therefore to (a) bring together a community of researchers and practitioners who are interested in exploring or showcasing the affordances of unmaking, (b) articulate the material and epistemological scopes of unmaking within HCI, and (c) reflect on frameworks, research approaches, and technical infrastructure for unmaking in HCI that can support its wider application in the field.