This paper reviews the literature, concepts, and operationalizations of the concept of entrepreneurial ecosystems. Despite some interest at the national level, entrepreneurship is understood to take place in localities or, at most, regions, drawing on local resources, institutions, and networks. Bibliometric evidence shows that usage of the term entrepreneurial ecosystem has overtaken other concepts, such as environments for entrepreneurship, which also highlight the mechanisms, institutions, networks, and cultures that support entrepreneurs. This review addresses several specific topics: the choice of scale, universities as ecosystem hubs, and how such ecosystems evolve. This is followed by suggestions toward an agenda for future research, placing particular attention on methodologies.