This dissertation analyzes the evolution of the Hashemite dynasty into two competing households during the late Ottoman period (1880-1919). Further, it explores how this rivalry between the ‘Awn and Zayd households led a member of the ‘Awn household to launch the Arab Revolt in 1916 and subsequently crown himself “King of the Arabs.” This project traces how these Hashemite households adopted two distinct political ideologies in order to legitimate their claims to the Amirate of Mecca. The ‘Awn cultivated and leveraged a cultural Arab identity wedded to Islamic unity through loyalty to the Ottoman caliph. This strategy proved most compatible with the political program of then Sultan-Caliph ‘Abd al-Hamid (1876-1909). In order to leverage their claim to the Amirate, the more senior Zayd household sided with movements calling for political reform to limit the power of the Sultan through a constitutional government. I argue that this divergent political evolution, coupled with changing political circumstances in the Ottoman Empire after the 1908 Revolution, eventually led one prominent Hashemite, Sharif Husayn ibn ‘Ali of the ‘Awn household, to embrace political Arabism. Having embraced an ideology that called for Arab political independence, he launched the Arab Revolt against the Ottoman Empire in 1916 with British and Arab nationalist support. With the outbreak of the Revolt and the subsequent nominal appointment of his Zayd rival to the Amirate of Mecca, Husayn then articulated a new Arabist and Islamic title for himself as the “King of the Arabs.” His formulation of this novel title and subsequent political program not only embraced essential elements of emerging Arabist discourses but also was ultimately shaped by his continued competition with a Hashemite rival throughout the Arab Revolt. Previous narratives of this period emphasize the post-1908 Ottoman government’s alienation of Husayn ibn ‘Ali and his subsequent attraction to British promises of support. In contrast, this dissertation highlights the significance of the rivalry between the two Hashemite households as a catalyst for Husayn ibn ‘Ali’s launch of the Arab Revolt and creation of the title, “King of the Arabs.” Whereas other scholars focus their analyses of this period only on formal negotiations, this project examines the writings produced by members of both the ‘Awn and Zayd Hashemite households to chart how the rhetorical and political rivalry of these households interacted with Ottoman, British imperialist, and Arabist trends. By locating the impetus for Husayn’s political development within an intra-Hashemite rivalry, this project offers a new insight into the dynamism behind the making of the Hashemite dynasty and the extent to which external powers (whether Ottoman, British, or Arabist) influenced these local politics during a critical moment in modern Middle East history.