The five oil-rich kingdoms of the Persian Gulf littoral have long faced a unique security dilemma, in that they are geopolitically vital but strategically weak states whose ruling regimes lay vulnerable to both domestic opposition and foreign aggression. How have these tiny states endured in the face of such challenges? Realist theories of international relations ignore domestic politics and instead point to Western hegemony: because these states carry critical oil reserves, Britain and the United States have ensured their survival through repeated interventions. The problem with such grand macrostructural accounts is that they ignore issues of domestic autonomy, in particular the capacity of these regimes to manipulate the international system and forge bargains with external patrons on their own terms. Rather than treat the littoral kingdoms as appendages to Western imperialism, we need to specify the historical process by which local rulers developed their sovereignty over time—that is, how they safeguarded internal territory, fended off domestic opposition, and evaded foreign predation. This paper responds to this challenge by comparing the evolution of the five Gulf sheikhdoms over the twentieth century. Draw upon new fieldwork combined with careful historical analysis, it argues that these dynastic regimes have been masterful diplomatic players, using foreign policy to reinforce their domestic security. Early on, Gulf sheikhs established patron-client relations with Britain in order to gain protection from regional powers like the Ottomans. Yet such cliency relations were informal, as these states never faced colonial exploitation or subjugation. Instead, domestic leaders negotiated maximal autonomy to govern their indigenous societies without foreign interference, only surrendering to Britain indirect mechanisms of control like military basing rights and diplomatic residency. Since the 1970s, Gulf rulers have replicated this pattern of “informal” empire with the US, giving America a similarly extensive network of regional bases and military privileges but allowing no intrusions into their internal politics. In essence, the clientelistic arrangement of informal empire is historically contingent yet logically appropriate. By surrendering a slice of territorial sovereignty to external patrons, Gulf leaders have effectively purchased the right to be left alone. They have not only secured international legitimacy and protection, but they have also carved out freedom to use newfound oil revenues to bolster traditional social interests while reconfiguring national economies to satisfy capitalist development. Such a strategy has minimized domestic opposition and produced long-term stability, resulting in the durable monarchical states that today crowd the Gulf littoral.