With its roots in both the New Wave theatre movement and in the traditional circus form, Circus Oz has, since its first shows in 1978, played a foundational role in the development of contemporary circus in Australia and internationally. This thesis draws on a series of extended interviews with key Circus Oz figures to develop, first, an historical account of the inception and the development of the company from the perspective of the practitioners involved, and, second, a thematic analysis of key aspects of the company’s work, again from the point of view of those working with the company over more than four decades of continuous activity. The key argument is that the great strength of the company—the determination to hold to the ideals with which the project started, and the experience and memories of those who worked with the company over the years, constituting a vast body of collective knowledge—is also a potential weakness, when that collective knowledge is lost, discontinued, or not articulated. The thesis not only documents and analyses this history, but on the basis of that analysis, identifies the fundamental elements of Circus Oz that made it an internationally successful company over such a sustained period. This thesis is presented in two parts: Part One presents the chronological history of Circus Oz to both record its history and to present the background to form a foundation for the analytical chapters. Part Two is broken into five themes, emerging from the interviews, which constitute the DNA of the company: the essential elements which, while subject to the vagaries of constant change, as personnel and external circumstances shifted, and as the company navigated the pressures of international success and growth, remained constants. The thesis argues that the essence of Circus Oz lies in the collective memories, practices, and aspirations of those who made, sustained, and constantly re-invented the company over a remarkable 45 years.