Immediately upon the creation of the League of Nations in 1919, the new organization became a primary target of petitions, protests and proposals of all kinds from the newly colonized Arab populations of the Mashriq. This paper uses the archives of the League of Nations and the Arabic press to investigate how the Arab encounter with the new League of Nations impacted the expression and development of nationalist rhetoric and organization in Syria, Palestine and Lebanon from the inception of the League in 1919 to its dissolution in 1946. Although infuriated by the imposition of European control over the Middle East, some Arab leaders in Syria and Palestine initially considered the League a potential ally in the war against imperialism, and some leading nationalists made early attempts to negotiate with the League for political rights against the colonizing powers. Similarly, minority groups in the Arab world initially tended to view the League of Nations as a possible creator of a particular vision of regional order in which they would have a defined, protected place within a post-colonial system of nation-states; Assyrian, Kurdish and Armenian communities scattered throughout the region of greater Syria all appealed to the League during its first two decades, seeing it as a potential reshaper of borders and nations. As the interwar period wore on and anti-colonial feeling escalated, however, Arab nationalism took on a new attitude to the League of Nations, one of fury and betrayal. In the 1930s, Palestinian Arab newspapers imprecated against what they had come to see as the League's quiet support for the European imperial project and its rather more vocal backing of European Zionist settlement. Around the same time, nationalist leaders in Syria were involved in a renegotiation of the terms of the mandate and the French administrative division of Syria into "statelets," with the League as arbiter of the dispute - a debate that produced furious anti-League rhetoric in Syrian nationalist newspapers and in popular political discourse. This history of the Arab relationship with the League of Nations demonstrates a shift from an initial wary interest in the League's principles to a permanent distrust of Western internationalist institutions. It also suggests some of the ways that the encounters of Arab political elites with the League helped to shape and sharpen national and ethnic corporate identities in the interwar Mashriq.