Legitimacy has emerged as a pivotal but often confusing construct in management research. The popularity of the concept and its widespread application to so many theoretical and empirical contexts has layered the construct of legitimacy with considerable surplus meaning. The object of this paper is to bring clarity and theoretical discipline to an important but misunderstood construct. We demonstrate through a description of the historical evolution of the construct that legitimacy has evolved in three distinct ways; from a focus on the property elements of legitimacy, to a focus on the process of legitimacy construction and finally to a focus on the cognitive practices by which legitimacy is negotiated.