My project is a history of international courts in Europe and the Americas in the first half of the twentieth century. Scholars usually date the origins of "world organization" to the two World Wars and the institutions that arose from them: the League of Nations and the United Nations. International courts, so this narrative goes, were merely the judicial branch of global governance, at least until the rise of international criminal courts after the Cold War. My project suggests this gets this history backwards. International courts, I argue, emerged much earlier, in different places, and in direct opposition to the idea of world government embedded in the League and later the UN. In short, these courts constituted the judicial organization of the world—a vision for judging the world not governing it. My project recovers a forgotten period in the late nineteenth and early twentieth centuries when jurists and politicians constructed international courts across Europe and the Americas. These courts sat at the apex of world politics. They claimed most of the world's states as members. They guarded their independence from other institutions, including the League in Europe and the Pan-American Union in the Americas. They ruled on the great political issues of their day: state sovereignty, Euro-American imperialism, the expansion of Nazi Germany. And, perhaps surprisingly, states almost always obeyed them. My project ends in a time and place long thought of as a beginning: the UN Conference on International Organization of 1945. There, a new international organization was brought to life, with a new international court subsumed within it. My project suggests an older, judicial organization was abandoned in its wake. Today, with the future of world organization in doubt, my project offers a new account of its foundations. We cannot understand what was gained in the postwar international order, I argue, without grasping what was lost for international courts.