In the post-9/11 era, the US officials posited an “Arc of Instability” sweeping across the Persian Gulf and providing a pithy justification for military intervention and escalation. Placed in historical light, this depiction of the Gulf and adjacent territories as volatile and a threat is not as innovative as the discussion of a New Middle East or the post-9/11 world suggests. In earlier decades the Gulf was the central node in the so-called “Arc of Crisis” and was often described as being “unstable” and “insecure” due to “pirates” and tribal conflicts. Prior to the rise of U.S. hegemony, moreover, the Persian Gulf was under the tutelage of British imperial officers, who identified the waterway and its littorals with the larger “Persian Problem” and Britain’s imperial rivalries and interests at the turn of the twentieth century. Across the twentieth century, this discourse legitimated both the British and the US to engage in imperial interventions, muscular foreign policy, massive military outlays, and alliances with foreign regimes. These understandings of the region have also been opportunities and constraints for local actors, from rulers to citizens, in their engagements with foreign powers and each other. Through a close examination of a number of key texts stretching from the last decade in the nineteenth century to first decade of the current century, I will examine how policymakers and academics have conceptualized and represented the Persian Gulf and how these geopolitical imaginaries utilize piracy, sectarianism, terrorism, and rogue states to fashion tropes of insecurity, instability, and anarchy. By analyzing the assumptions undergirding these geopolitical imaginaries, I will trace the extent to which there have been continuities and discontinuities across the long-twentieth century in how the Gulf has been positioned in geopolitics and how politics in the region have been interpolated into global hegemonic orders.