This paper begins by describing (in part A) the UK concept of social enterprise and how it is operationalised (section A.1); this is followed by an overview of the challenges of estimating the population of social enterprise in the UK, despite or because of different government-sponsored surveys (section A.2); this first part concludes with a review of the evolution of policy discourse for social enterprise (section A.3). The second part of the paper goes on to describe (sections B.1 to B.4) the different models that have evolved from different origins in the UK (with the main emphasis being on experience in England); in order to contextualise an understanding of these models, it describes three fields (section B.5)—work integration, community development, and public services; these illustrate the fluidity of models in the UK, where typically different models may be found within each field. Finally, Part C describes at a general level the relevant institutional frameworks and trajectories of the main social enterprise models