The term ‘critical design’ has seen increasing usage in recent years, however the literature in the field to date has not deeply interrogated the concept of critical design in relation to established theories of critique. So that critical design as a concept and as a practice might become more fully thinkable in terms of its particular critical potential, this chapter synthesises current discourse on critical design with established theories of critique from the domains of political and social inquiry. Notably, the chapter seeks to unshackle the term from its common association with the domains of industrial design, interaction design and electronic product design in the recent UK tradition, and draws other design disciplines and other types of design practice into the debate. Employing a genealogical approach, the chapter traces the roots of critical design, as an interrogative and emancipatory practice, back to continental Enlightenment philosophy, before synthesising contemporary discourse on critical design with key concepts from the fields of design studies, Marxist philosophy and post-Marxist political theory. Building upon this, the chapter sketches the particular significance of design as a type of critical practice: design, it is argued, is well placed to be a technique of enlightenment because of its disposition towards future thinking. The chapter does not discuss examples from practice in detail, and so invites future applied interpretations. The chapter will be of relevance to research in design studies, and it will be of particular interest to scholars and practitioners concerned with the politics of design across disciplines.