When philosophers and sociologists have sought to define ‘religion’, their definitions have invariably stumbled in the face of counter-examples. Some definitions have been too exclusive—failing to include non-theistic religions. Some have been too inclusive—failing to exclude non-religious ideologies (such as Marxism). This chapter takes religiosity to be conceptually prior to religion. Accordingly, a definition of religiosity is first proposed, which in turn allows for a definition of religion that seems immune to any obvious counter-example. Religiosity, it is argued, demands community, faith, and imagination. Religions are systems of ideas and/or practices that call for religiosity in a way that non-religions do not.