This article traces the genesis of the principle of legacy as it has featured in Olympic discourse, and become enshrined in the expressed philosophy of the International Olympic Committee (IOC), so shaping elements in the process of bidding by cities to stage the Olympic Games, in both their winter and summer manifestations. The article shows how Olympic bidders have increasingly mobilised the idea of legacy, and how event by event over the last quarter of a century, evaluation of the significance of an Olympic Games has been centrally shaped by the legacy debate, in a multitude of applications and contexts. Particular aspects of legacy are focused upon, with reference to new studies, from city impacts to volunteers and workers, spatial politics and communities to gender discourse, and protest and publics. The article is flavoured by a running commentary on legacy claims by academics, politicians and IOC careerists concerning the London 2012 Summer Olympics, and considers the bidding rhetoric of cities beyond Rio de Janeiro 2016, through to Tokyo 2020. In conclusion, it is argued that despite the embeddedness of the legacy idea in Olympic discourse, the reality is that legacy will prove elusive without long-term planning before Olympic events, and remain unproven without systematic post-event research over realistically extended periods. Critical social science remains essential to such an understanding of the gap between legacy claims and the realities of the recurring Olympic narratives