Entrepreneurial action is the central idea that motivates the study of law and entrepreneurship.1 Promoting entrepreneurial action is a fundamental goal of the US legal system.2 Although existing definitions of entrepreneurial action are legion,3 these definitions have been difficult to operationalize in a legal context because the application of legal rules does not turn on whether someone is acting as an entrepreneur.4 In this chapter, therefore, we offer a new conception of entrepreneurship that is consistent with understandings of entrepreneurship in other disciplines while being accessible and meaningful to legal scholars. We assert, in simplest terms, that the core function of entrepreneurs is to challenge incumbency.