This article provides an overview and concise analysis of the often underappreciated bilateral security and defense agreements that the United States entertains with a significant number of countries around the world. It sets out by emphasizing the role of the United States in sustaining the world order at a systemic level and notes that Washington’s bilateral relations, albeit forming a significant part of the overall security and defense arrangements, receive much less attention than multilateral alliances and systemically conditioned alignments. After briefly reviewing recent literature on this subject, the article examines the process by which the United States enters into agreements of varying legal and political status, and then discusses the ramifications and limitations of the respective types of arrangements. In turn, the article examines formal bilateral treaties (mainly with East Asian states), politically motivated security and defense agreements (mainly in the wider Middle East), and, lastly, executive agreements initiated by the presidential administration, the Defense Department or the State Department. The article ends by suggesting that the administration of Donald J. Trump—given campaign statements and the first six months in office—is less likely than many of its predecessors to enter into new agreements and formalize existing alignments, and that the viability of existing ones may become increasingly dependent on America’s counterparts demonstrably living up to their end of the bargain.