Russian foreign policy from the mid-1960s has vacillated between periods of expansion and retrenchment in which the military and diplomatic reach of the state has extended to continents or been retracted to very modest conceptions of national defense. During this period, the financial centrality of energy exports has come to dominate the Russian economy, leading scholars and observers to draw a causal link between the two: as energy revenues go up, expansionism does as well, while declines in revenues lead Russia to behave less assertively. This dissertation outlines an alternative argument for petrostate foreign policy in which positive or negative revenue environments determine the menu of policy options available to policymakers, but that internal politics determine the content of those foreign policy choices. I argue that foreign policy choices are conditional on the mediating political institutions and circumstances existing at the time of booms and busts, namely that how energy revenue shocks affect foreign policy decision-making in a petrostate after a revenue shock depends on the political environment before the shock. The petropolitics foreign policy theory thus provides insight as to when the expansionism might occur. By focusing on revenue yet allowing politicians to retain agency, this “petropolitics” foreign policy theory links structural theories of foreign policy to leadership-driven models of political decision-making. This petropolitics theory then reassesses Russian foreign policy by analyzing leadership tenures from Leonid Brezhnev to Vladimir Putin. I show that Soviet expansionism in the Third World in the 1970s was not simply because of a positive revenue shock, but because of Brezhnev’s political weakness after his installation in a palace coup. Similarly, I show that Mikhail Gorbachev’s retrenchment of foreign policy commitments arose not solely from a lack of energy revenues, but from his political strength in light of the poor performance of his predecessors. Finally, I show that Vladimir Putin’s selective expansionism and retrenchment emerges in a skillful consolidation of domestic political strength, a fortuitous influx of energy revenues, and a willingness to change foreign policy strategies to serve a single preference of maintaining power. / text