The Indo-Pacific region's security landscape is unfolding in highly uncertain and potentially explosive ways. The postwar American-led network of bilateral alliances-underpinned by concrete guarantees of extended deterrence and containment-is now yielding to a more diverse set of alignments and coalitions to manage an increasingly complex array of regional security issues. Multilateralism and minilateralism have emerged as two increasingly prominent forms of such cooperation. Minilateralism's informality and flexibility appeals to those who are sceptical about multilateralism's traditional focus on norm adherence and community-building even as great power competition in the Indo-Pacific is sharply intensifying. However, minilateralism's track record in the region is underdeveloped. The potential for this policy approach to be applied by the United States and its regional security partners as an enduring and credible means of diplomatic and security collaboration in the region will remain unfulfilled as long as the Trump administration's own geopolitical orientation remains uncertain.