This conceptual paper proposes a new framework for evaluating the two central facets of Olympic Games performance: their delivery and their legacy. This framework, which I call the “Olympic diamond”, is based on classic concepts of managerial performance and public policy evaluation, developed over many years by managers and political scientists to measure public action. Indeed, the Olympic Games, which are now attributed seven years before they take place, have become a sort of public policy/programme or, more accurately, a partnership between the public authorities and private actors within a given territory (city, region, country). This partnership requires public bodies to work closely with private non-profit organisations and for-profit companies over a period of 12 years or more to implement a vast series of measures. Section 1 shows how the Games have evolved from a purely private affair to a true public policy, and discusses what is meant by Games performance. Section 2 reviews recent attempts to measure or evaluate this performance. The final section presents an approach to evaluating Olympic performance – the Olympic diamond – and describes its four vertices and five evaluation criteria, drawing on the 2012 London Olympics to illustrate how this framework can be applied. The conclusion discusses the Olympic diamond’s potential for evaluating and comparing other editions of the Games or other Olympics-related projects and facilities.