For many years, the U.S. military presence in Southeast Asia (SEA) has served as an important stabilizing factor in region and has allow countries in the Association of Southeast Asian Nations (ASEAN) to sustain high economic growth, and develop social and political stability. With the loss of the Philippine bases in 1992, the only forward deployed U.S. forces in the Asia-Pacific region are located in Japan, the Republic of Korea and Hawaii. At the same time, the U.S. military in SEA is maintained through the use of port facilities and a multitude of bilateral security relations, and military exercises with individual ASEAN states. in the twenty-first century, ASEAN will continue to be confronted by a number of security concerns. This study shows that the significant threats facing the region are an aggressive and assertive China, conflict in the South China Sea, and an unstable Indonesia. In view of these security concerns, the study argues that a U.S. military presence in SEA is still necessary in the twenty-first century. Maintaining such a presence will yield significant benefits to the U.S. and ASEAN. However, the continued presence of the U.S. military in SEA is expected to face greater challenges due to lower military resources and support, as the U.S. finds itself increasingly embroiled in conflicts worldwide. The study proposes three possible options in which a continued U.S. military presence in SEA can be maintained, namely, maintaining the status quo, an increased presence and a surrogate presence. On balance, maintaining a surrogate presence, by empowering a suitable country within ASEAN, presents the best option for the U.S. and ASEAN.