What explains the lack of democracy in the Arab Middle East, when so many other, less wealthy regions of the world have democratized over the past five decades? This thesis engages with each of the major explanations for the "Arab democracy deficit"--Islam, the "oil curse," authoritarian statecraft, and external intervention--but argues that there is a more fundamental culprit for the region's woes: the weakness of state-based nationalism. At a time when nationalism is increasingly seen as synonymous with exclusion and discrimination, such a finding may strike many observers as counterintuitive. However, this thesis theoretically and empirically demonstrates how healthy, state-based nationalism can provide the societal cohesion needed to establish liberal governance. It then offers in-depth analyses of the development of national identity and democracy in eleven separate Arab countries, arguing that the rise of regional Arab nationalism in the 1950s severely undermined the development of state-based nationalism (wataniyya), and laid the groundwork for decades of instability, civil strife, and oppression. Fortunately, the examples of Tunisia and Lebanon--and to some extent Jordan and Morocco--demonstrate that wataniyya can lead to much more democratic outcomes when properly nurtured.