American labour historians have long considered the Order of the Knights of Labor to be one of the most important labour organizations of the late nineteenth century. Yet they have tended to view the Knights as an exclusively American, and perhaps also a Canadian, order. This article argues that the Knights of Labor must be considered as an international and not merely North American institution. This also has implications for the history of international labour organizations, a subject which is almost exclusively concerned with European bodies. In view of the Knights’ activities outside North America, this history must be altered, if not necessarily overturned, if we place the Knights in the history of international labour organization. This article first integrates the Knights within the chronological narrative of international labour organization. It then compares the Order with other international labour institutions of the nineteenth century. In the process, it argues that the Knights of Labor should be considered the most significant international labour body active between the famed First and Second Internationals, and for this reason deserves to be recognized as the First-and-a-half International.