This chapter articulates the alignment challenge in grand strategy and foreign and security policy of Southeast Asian states. It explores the historical legacy and complexities of Southeast Asia alignments across centuries, which make it difficult to pursue clear alignment choices with respect to major powers articulated in international relations approaches including balancing against a threatening power, bandwagoning with it or adopting a middle position around neutrality, non-alignment or hedging. The chapter places an emphasis on the ability and willingness of regional polities to exercise their own agency through subtle shifts amid domestic, regional and international changes and pressures—with varying degrees of connectivity and success not just with major powers but also simultaneously with respect to actors within their borders, non-state actors and wider networks. It also assesses the value and limitations of current internal and external approaches used to analyze Southeast Asia alignments, which arguably reinforces the need for refinement in existing explanations as well as the development of newer models and approaches.