The historian of Southeast Asian Buddhism faces many questions regarding Buddhist identity. Using the case study of Arakan (western Burma), two critical questions are pursued in this dissertation: why did Theravada Buddhism emerge as a religious identity for the majority of Arakanese and why did this religious identity develop into Burmese-Buddhist religious communalism? The prevailing literature regarding Arakanese history accepts uncritically a primordialist view of an ever-present Buddhist religious identity in Arakan from the pre-fifteenth century, that this religious identity was the chief means of collective action by Arakanese throughout the early modernperiod, and that it always involved social exclusion of Muslims. After examining Burmese-language palm-leaf manuscripts from collections in Burma and the British Library, royal orders and court treatises, and contemporaneous Portuguese and other foreign accounts, I concluded that these assumptions are incorrect. Burmese Buddhist communalism was clearly a phenomenon of the nineteenth and twentieth centuries and generally did not define group action in preceding centuries. This dissertation makes two inter-related arguments. First, the Burmese Buddhist religious identity developed from a complex array of influences. Ecological, climatological, social, economic, and political factors all played important roles in determining the direction of and response to religious developments. Thus, Theravada Buddhism was not the ancient and monolithic religious identity that some have interpreted it to be. Rather, the Buddhist religious identity as it has emerged today developed gradually, and primarily from the end of the eighteenth and into the nineteenth centuries, during the periods of Burman and British rule. This was true also of the Arakanese Muslim identity. Second, Burmese-Buddhist communalism developed out of competition between Muslims and Buddhists for new agricultural lands and attempts to survive on shrinking land plots in the British colonial economy. British colonial authorities also reduced the vitality of patron-client relationships which meant the emergence of religious leaders as organizers of rural communities for collective action.