Luxury is one of the key words of our time, driving a multimillion dollar global industry, and used ubiquitously to describe exclusive objects and aspirational lifestyles. However, defining the concept in concrete terms is more elusive and problematic. Part of the definitional problem lies in the longer history and use of this concept. This article looks at luxury's longue duree, and aims to clarify some common misunderstandings around its use. It reminds us that, in its origins, luxury was not a term to describe consumption by elites, but one used to denigrate the consumer practices of newly emerging wealthy classes. It argues for four key phases in the development of the concept: the ancient world, the early modern period, the eighteenth century, and the late twentieth century. In particular it focuses on early modern Italy as a crucial period and place in luxury's defining moments, yet one that is often overlooked. It was the Italians who were the first to revive the ancient use of luxury as a term of denigration for the aspirational consumption of non-elites, and it was also the Italians who were the first to invent a new word in the vernacular to describe this consumption - lusso, or luxury. Luxury as word, concept, and practice is a contingent historical product which evoked and continues to evoke ambivalent and strong emotions in every period.